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An Experimental Investigation Of The Dichotic Application Of Delayed Sidetone And Masking Noise

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An Experimental Investigation Of The Dichotic Application Of Delayed Sidetone And Masking Noise

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Content AN EXPERIMENTAL INVESTIGATION OF THE DICHOTIC APPLICATION OF DELAYED SIDETONE AND MASKING NOISE by Edward William Gibbons A Dissertaion Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (Speech) June 1959 UNIVERSITY O F S O U T H E R N CALIFORNIA G R A D U A T E SC H O O L. U N I V E R S I T Y P A R K L O S A N G E L E S 7, C A L I F O R N I A This dissertation, ■ written by .......E.dw&Ta. I'll 1 la m. X I lb b . o . n s..... under the direction oj hXJei...Dissertation C o m mittee, and approved by all its members, has been presented to and accepted by the Qradante School, in partial j nip 11 me nt oj requirements for the degree of D O C T O R O R P H I L O S O P H Y Dean Date.....i/iay...la a a......... DISSERT ATI O N CO A1MITTEE C . h a i n i u i n A C KNOWL E DGM E ITT Appreciation is gratefully expressed to the Veterans Administration for the opportunity to participate in an important, growing medical program; to Dr. Joseph A. Gengerelli, Consult ant in Psychology to the Veterans Administra tion, for his valuable suggestions regarding the statistical treatment in the experiment; and to my wife, whose understanding and unfailing kindness made possible the comple tion of this report. TABLE OF CONTENTS Page ACKNOWLEDGMENT ........................................... ii TABLE OF CONTENTS.................. iii LIST OF T A B L E S ........................................... v Chapter I. THE PROBLEM, DEFINITION OF TERMS, AND SIGNIFICANCE .................................... 1 Statement of the Problem ..................... 2 Definition of Terms ..... 3 Significance of the Problem.................... 5 II. REVIEW OF THE LITERATURE........................ 13 Side t o n e ........................................ 13 Delayed Sidetone ............................... lb The Masking of Speech.......................... 30 III. THE EXPERIMENT.................................... 39 Experimental Design ............................. 39 Subjects........................................ 41 Materials ...... 43 Procedures...................................... 54 IV. PRESENTATION AMD INTERPRETATION OF THE DATA . . 58 Statistical Procedure .......................... 58 Analysis and Interpretation of the Data . . . 59 iii iv Discussion.................................... 78 V. SUMMARY, CONCLUSIONS AND IMPLICATIONS.......... 81 Summary......................................... 81 Conclusions.................................... 82 Implications .................................. 84 BIBLIOGRAPHY ........................................... 87 APPENDIXES ............................................. 95 A. Clinical Information for the Unilaterally Deafened Group .............................. 96 B. Tables of Elapsed Oral Reading Times Obtained in the Experiment.............................. 99 C. Preliminary Reading Materials ................... 102 D. The Reading Passage.............................. 104 E. Description of the Masking N o i s e .............. 113 LIST OF TABLES Table Page 1. Group Reading Times in Seconds ................. 60 2. Analysis of Variance of the Elapsed Oral Reading Times of the Total Population under Four Treatment Conditions .... ................. 61 3. Summary of the Analysis of Variance of Elapsed Oral Reading Times of the Normally Hearing and Unilaterally Deafened Groups Treated Independently under Four Treatments .......... 62 4. Analysis of Variance cf the Elapsed Oral Reading Times of the Combined Groups under Treatments Experimental I and I I ............................62 5. Mean Differences between Times Obtained in Total Dst Pro sen tation with the Unilaterally Deafened Group ............................... 63 6. Analysis of Variance of Four Treatments; Experi mental I and II of the Normally Hearing Group and Combined Dst Times to the Better Ear and Poorer Ear of the Unilaterally Deafened Group . 64 7. Analysis of Variance of Three Group Treatments: Experimental 1 and Experimental II of the Normally Hearing Group and Combined Dst Times to the Better Ear of the Unilaterally Deafened Group................ 65 8. Reading Times for the Sub-divided Unilaterally Deafened Group.................. 66 9. Difference in Reading Times for the Unilaterally Deafened Group between the Two Conditions; Dst to the Better Ear First and Dst to the Poorer Ear First........................................ 67 10. A statistical Comparison of the Difference of the Differences in Reading Times between Condi- v vi tions: Experimental I and Experimental II when Dst Is Presented to the Better Ear First and When Dst Is Presented to the Poorer Ear First for the Unilaterally Deafened Group . ......... 11. Analysis of Variance of Combined heading Times of Treatments Unimpeded I and Unimpeded II for the Formally Hearing arid Unilaterally Deafened Groups ........................................... 12. Significance of the Difference betvveen Means of Treatments Unimpeded I and Unimpeded II for the Formally Hearing and Unilaterally Deafened Groups ........................................... 13. Analysis of Variance of Three Treatments v;ith the Unilaterally Deafened Group: Unimpeded I, Unimpeded II and Total Heading Times of Dst to the Poorer L a e ........... ...................... 14. Reading Time Differences iii Seconds between experimental I ano rxpex'imontal Ir treatments of the normally Heating Group ................ lb. Geological Diagnoses and Speech Audiometry Results for the Unilaterally Deafened Group lb , r 1 ap se o. ur a I Re ad r rig i r me s UP t a i nc d iox the normally Hearing Group .......... 17. Elapsed Oral Reading limes Obtained for the Unilaterally Deafened Group ................ 68 71 72 7b 77 97 100 101 CHAPTER I THE PROBLEM, DEFINITION OF TERMS, AND SIGNIFICANCE It has been generally recognized that more and better objective tests of non-organic deafness are re quired which can be easily administered, repeated, and which can be understood by professional personnel in relat ed disciplines, such as lawyers, psychologists and others. Delayed sidetone testing procedures are beginning to indi cate that this is a valuable objective audiometric method. Delayed sidetone has the advantage of being relatively simple to give, rnerely requiring an agreement on the part of the subject to read (35:198). It fulfills the require ment for the testing of communication ability called for by Glorig: "The most important means of communication is speech, therefore, a Lest which uses speech as a stimulus is essential" (33:590). One delayed sidetone application, that employing a dichotic presentation, is particularly useful, especially when one normally hearing ear exists, since by testing each ear independently, while masking the opposite, it becomes possible to use the subject as his own control, a valuable technique recommended by Harris (37:700). Clinical application of delayed sidetone during the past decade has demonstrated the stability of the technique in bilateral presentation when there is symmetrical hearing in both ears. One limitation exists in bilateral presenta tion when such symmetry does not exist. In these cases, results of delayed sidetone testing are reflective of hear ing in the better ear only. Additional, information is needed regarding the testing of individual ears as well as the use of unimpeded oral reading times, 'which 'will serve as a reference for determining the existence of delayed sidetone involvement. Statement of the Problem The major purpose of this study was to determine what, if any, Is the difference in elapsed oral reading times of selected prose passages of normally hearing and unilaterally deafened subjects which can be attributed to the dichotic application of delayed sidetone and masking noise. Subsidiary problems studied in conjunction with the major element of study were the following: 1. What, if any, is the difference in elapsed oral reading times of selected prose passages of normally hearing and unilaterally deafened subjects before the dichotic application of delayed sidetone and masking noise? 2. What, if any, is the change in the elapsed oral reading times of selected prose passages of normally hearing and unilaterally deafened sub jects following the dichotic application of delayed sidetone and masking noise? 3. To what extent, if any, does adaptation occur during the second condition of dichotic appli cation of delayed sidetone and masking with normally hearing and unilaterally deafened subj ect s? Definition of Terms Delayed sidetone For the purposes of this study, delayed sidetone is defined as the disruption, by means of extra-subject pro longation, of the hearing of one’s own speech. It is com monly referred to as dst, At supra-threshold levels of presentation, dst affects speaking in terms of alterations of rate, rhythm, intensity, pitch, quality and articula tion. Dichotic Dichotic stimulation refers to the simultaneous stimulation of both ears, but with a different stimulus in each ear (14:451). By contrast, diotic refers to the stira ulation of both ears by the same stimulus. Elapsed oral reading time For purposes of this study, elapsed oral reading time is defined as the total time, expressed in seconds, required to read a given passage which encompasses all pauses and vocalization made during the reading task. Masking Whenever one sound causes a second sound to become less audible by coexisting with it, the phenomenon demon strated is called masking. Unilateral deafness For the purposes of this study, unilateral deafness is defined as that type of deaf ness where one ear falls within the normal range in the speech range with an SKT of 10 db or better in the good ear with no single frequency from 000 to 0,000 cos. loss acute than 10 db, and a hearing loss of 30 db or greater in the good ear. A single standard term is needed. Synonymous phrases found in the literature include delayed side tone (18), delayed side-tone (21), speech feedback (51), delayed speech feedback (67), delayed auditory feedback (64), delayed-feedback test (9), and delayed speech play back test (39). Certain authors have used several of the above terms in a single paper. In agreement with Black’s use of the term in later work as well as its use by Tiffany and Hanley, the term delayed sidetone has been chosen for use in this paper. Sidetone is a standard term in communications engineering. Delayed sidetone includes both concepts of talking and listening and is not restricted to either the speech or auditory aspect alone. This terra also lessens the con flict with the standard term used in speech pathology, delayed speech, which has been defined as; "Delayed speech: failure of speech to develop at the expected age; usually due to slow maturation, hearing impairment, brain injury, menta 1 retardation, or emotional disturbance1 1 (16:54). S ignif icancc- of she Pr obi era The major significar.ce of this study lay in the potential for refinement of existing delayed sidetone audiometric techniques used in evaluating difficult cases of non-organic deafness. This technique is one method of specialized audiometry in use in the V. A. Audiology pro gram, with cases which are eventually processed through a medico-legal rating resulting in the award, or denial, of monthly compensation payments. This medico-legal testing is characterized by a high incidence of exaggeration and because of this element, more objective tests are being developed, among them delayed sidetone. Large sums of money awarded as monthly compensation are involved, as well as medical treatment rights for the individual awarded a service-connected disability rating; related areas include social, economic and vocational problems and the use of prosthetic devices. This evaluation and adjudication proc ess is a complicated one, and is one element in a much larger program of veterans’ benefits. Disability which is demonstrated in Veterans Admin istration medical evaluations, in order to be granted serv ice connection or aggravation, must have been incurred or aggravated in service. This applies to ail categories, including hearing disablement. Glorig, in describing the development of aural rehabilitation services during V.'orld War II, stated that the evaluation of hearing acuity in military service has long beer, a probJem (33: D9C). One of the basic causes of the confusion surrounding the proper evaluation of hearing acuity both on entrance into and dur ing service v;as the use of spoken and whispered voice tests which he considers useless for determining line of duty, progression, aggravation, eligibility for retirement, or amount of disability. If any of these are to bo determined properly, reliable and consistently repeatable tests must be used. This led to methods of testing nova in use. Fournier, in writing of the discrepancies existing when comparisons were made of the results of spoken and whispered voice tests with later audiornetric results, stated that the otologist, armed with his voice alone, and with the classic instrumentation, was led to admit the 7 existence of deafnesses which, in reality, were either much less pronounced or sometimes entirely simulated. In these cases, the error was always iii the same direction, and it was often considerable (67:10). Calling attention to the fact that this problem of non-organic hearing loss knows no limitation, of national bounds, Fournier referred to the Russian, Zilboory, who stated that the frequency of the psychogenic factor was found in 60 per cent of deafness acquired in combat (67:5). In analyzing the possible cause of the high percen tage of non-organic deafness found in the course of hos tilities, Fournier stared thar it might be due to the "indulgence of experts" (o7:6). In describing malingering where monetary awards are a consideration, he proposed the term "sinistrosis," which he dcfined as the orientation of the mind towards the idea of damages (u>7:4 ). Johnson stated that there has been an increase from 10 to 50 per cent in the problem of non-organic deafness since the end of 'dorId War II among American veterans (39:155). In developing a rationale for the payment of one lump sum a'ward, he goes on to attribute the rise in the incidence of cases of non-organic deafness between the end of v/orld War II and the present time to the following three causes: the monthly compensation policy, the conversational voi.ee hearing test and inadequate orientation and counseling at Ine onset of the hearing loss (39:156). Continuing 'with i his discussion of the problem of evaluating the case of non-organic deafness, or of making the distinction between the volitional and non-volitional aspects of a case, Johnson stated that contrary to rather general belief, most persons manifesting a functional loss, whether the loss is of conscious or unconscious origin, will resoond to audio metric examinations in essentially the same manner. Fournier was in agreement with this statement when he said that there are no functional tests which permit the differential diagnosis of this deafness; psychogenics and malingerers react to the tests iii exactly the same way (67:7). Although the type of functional case referred to above is seen most frequently in clinics which are a com ponent part of a larger medico-legal setting, there none theless seems to be a growing awareness of the problem in other types of clinics. Johnson stated that in a question naire study of functional deafness in adults as diagnosed in 3 0 leading public Audiology Centers, Doerfler reported that 63 per cent of the centers found no cases of func tional deafness, while 37 per cent reported an incidence of frorn 1 to 6 per cent. 0n 1 y 10 per ceist of the centers re ported an incidence in excess of 6 per cent. However, Johnson suggested that in addition to his three causes for the increase in functional deafness, improvements and de velopments in testing equipment, as well as increased 9 experience with the problem on the part of examiners, have made easier the diagnosis of non-organic hearing loss, and consequently increased the percentage of functional cases reported (39:158). .suggesting later that clinicians be assigned to evaluate the true organic hearing level of cases simulating deafness, Johnson; stated that if such practice were put into effect, clinical awareness would be heightened and the incidence of functional deafness among the hard of hearing public at large would be found to be greater than presently suspected (99:163). Ihere are certain cases, fortunate1y few in number, where it is impossible to achieve results of audiometric tests which agree among themselves. Consequently, there is on occasion a need for the subjective opinion of the expert 'where there is clear-cut and reasonable evidence of exaggeration. Constant effort, however, must be made to reduce the need for such subjective evaluation and to im prove objective clinical audiometry. In delayed sidetone, we have a promising objective method which Johnson has called an excellent tool for use with functional hearing loss problems (39:166). Delayed sidetone testing is probably the most ob jective method available at this time for evaluating non- organic elements in auditory testing. There are very few cases, if am/, which do not demonstrate speech involvement resulting from dst when it is presented in controlled 10 fashion. A certain number ox oases may not have striking speech changes, and others may not show pronounced prolong ation of oral reading, but it is rare that subjects do not exhibit one or other of these effects. Although more re search is needed in order to refine dst for more special ized application, nonetheless it has been used to advantage in the Audiology clinic v/ith certain types of cases. The most obvious type is that which presents no measurable hearing at the limits of audiornetric equipment. If the hearing is more acute than is at first claimed, dst makes it possible to demonstrate interference at levels indicat ing that measurable hearing does exist. This is also true with cases where the dst involvement occurs am a level dif ferent from the one given in standard audiometry, where the subject claims a certain level of hearing disability but responds to dst at 1evels showing be11or hearing, Another advantage to dst generally in medico-legal evaluations is that the taped recordings of the subjects’ speech perform ance can become a part of the record for future reference. The objectivity of dst testing should have an effect in minimizing the problem of the changing of disability ratings from examination to examination, based on the fluctuation of various examiners’ reports, a condition which particularly prevailed when spoken and whispered voice test results were used in adjudicating these claims. Adverse effects resulting from unneeded surgery, rehabilitation, 11 issuance of hearing aids, as well as social and psycholog ical imbalance, should also be reduced. The significance of this study lies mainly in the information which should emerge regarding difference in performance between normally hearing and unilaterally deafened subjects showing true organic hearing losses, under the dichotic application of dst and masking noise. This information should be of value- in managing cases feigning unilateral deafness. Information from this study should also er.har.ee the understanding of the theoretical implications of the relationship botweer. other audiometric test procedures and dst. Also, information gained from the study should have direct bearing upon the refinement of existing test procedures and aid in the development of new test procedures. A secondary consideration, but one of importance in the clinical application of delayed side tone , will be the determinal ion of 'whether or not presenta tion ordew has an effect on the oral reading rates of these groups. Inf ormation regarding the advisability of obtain ing unimpeded oral, reading times in conjunction with de layed sidetone reading times should be derived from the study, including the order of testing. In this connection, information on any possible effect on unimpeded reading times caused by previous application of delayed sidetone should be forthcoming. finally, results from this experi ment should prove of value regarding the question of the 12 use of masking in dst testing as it is used in other audio metric procedures, such as bone conduction testing and in speech audiometry. CHAPTER II REVIEW 0Er THE LITERATURE The discovery of delayed sidetone has been attribu ted to Lee in 19b0 (41). The phenomenon, however, had been recognized by the Beil Telephone Company previous to this date, and because of its detrimental effect on telephone transmission, had caused modification of circuitry, in order to improve handset efficiency. S idetone Sidetone is a standard term used in communications engineering. It is described as a small current propagated back to the talking station, which is heard as a distinct echo if the time of transmission around the circuit is great enough (71:27b). There are a number of effects due to sidetone in the telephone, A speaker normally gauges the volume of his speech over a telephone line by the portion of sound which reaches his ears. If the sidetone is high in volume, the speaker will tend to lower his voice, which may make the re ceived energy at the far end too low. Another effect is the reduced sensitivity of the ear immediately after talking over a set with considerable sidetone. The sidetone may 13 14 be rather large in comparison with the energy received from the far end, and the alternation of loud sidetone with less loud far-end conversation may be disadvantageous to the proper understanding of the received conver sation (73:16) , The time of telephone delay is not constant, and has been described by Pierce and David in the following manner: Vinen we speak into a telephone headset we can hear a bit of our own voice in the receiver as we speak. The echo arises in much the same way. Cur voice passes over the sending wire pair to the distant sta tion. There the electrical equipment feeds some of the incoming speech onto the return pair, and thus the talker hears an echo of his own cords fed back to him, delayed a time corresponding to twice the distance be tween stationso (11:266) from the standpoint of transmission, the major development in telephone station circuits has beer, the introduction of the anti-sidetone circuit. The purpose is to reduce the amount by which sounds entering the trans mitter are reproduced in the receiver of tire same set. The first anti-sidetone circuit in commercial use 'was invented by C. E. Scribner in 1393 (70:347). The anti-sidetone circuit as compared with the sidetone circuit reduces side tone on the average by about 10 db (72:2). During the speaking process itself, and without reference to headphones or amplification, two auditory pathways operate in the individual. They are: (1) the air conduction pathway, wherein the sound travels from the vocal cords past the resonating cavity of the mouth, radi ating externally around the head and returning to the outer 15 auditory canal; (2) the bone conduction pathway, which goes directly from the vocal cords internally to the cochlea. ■Stromsta has estimated the minimum propagation time for air-conducted sidetone to be 0.001 second and for bone- conducted sidetone to be 0.0003 second. These times refer to the normal return of the speaking voice without the interference of abnormal delay (66). Delayed Sidetone The original reports by Lee on delayed sidetone contained descriptive material without any statistical analysis, but only general observations the author had made concerning the e-ffeet, particular 1 y xhe inf 1 uencc on a speaker of a simultaneously monitored delayed sidetone of speech (38, 42, 43). Lee called attention to the fact that "the effect on speech is involuntary and induced with little or no regard to previous conditioning or the sub ject's will to oppose the influence of the feedback" (42). He further suggested that the dst effect is critical with respect to volume of feedback and amount of delay of the sidetone. According to Lee, "while the artificial stutter is the most striking reaction, it is the less spectacular speed governing effect which probably will provide the most useful information" (43). Huntington conducted a study which investigated the relationship between auditory ability and speech perform 16 ance during delayed sidetone (64). Seventy-five adult males were the subjects. Elements of study included time, audi tory memory span, pitch, tonal memory and rhythm. The results were not conclusive. Black conducted an experiment investigating the ef fects of abnormally delayed sidetone upon the rate and intensity of speech (21), it is greater interest lay in studying thc cffects upon rate of reading. Intensity was measured incidentally. Each of twenty-two subjects read eleven series ox snore phrases, a serre s conraining rive b-syllaole phrases. ho concluded chat the general effect of delaying the sidetone is a retarding of speech, and that delayed sidetone affects vocal rate and intensity during reading. A number of research workers in the field have set about constructing their own "feedback machines," usually on the basis of designs published by iV.arple and l.iorrill (66). These adaptations have generally been unsatisfactory in the clinical setting. Tiffany, Hanley and Sutherland set out to devise an adapter for controlling variable sidetone delay by adding separate components, such as guide posts, an adjustable idler pulley and a swinging arm assembly (67), They list as drawbacks a tendency toward interference with tape speed and speed regulation, and the fact that the playback head shield is not usable when the delay mechanism is in 17 place. Rawnsley and Harris conducted a comparative analysis of normal speech and speech with delayed sidetone, making use of sound spectrograms and found that this technique gave a readily observable nature to the effect and that vocal rate „ duration, and intensity could be easily meas ured by this means (69). Tiffany and Hanley conducted an experiment designed to provide additional information regarding the speed governing effect reported by Lee (36). They also observed the responses of subjects to sidetone levels over the lower range of intensities, from 10 to TO db above threshold. Under the conditions studied, the authors stated that there seems to be some slight effect for sidetone levels as faint as 10 db above threshold. They concluded that judgments of over-all effects of speech breakdown are no better than rate measures alone. In order to determine vocal rate-duration and inten sity correlates of dst, with the time of feedback and read ing materials variable, Spilka used longer reading passages than had been employed in previous research and presented one condition per subject (bl). In general, his findings were similar to those obtained by other research workers, except that the results were more exact. Ho relationship was found between the length of delayed feedback time interval and the changes which occurred in average syllable 18 duration, per cent phonation time, and mean vocal intensity. An experiment was conducted by Peters in which the effects upon oral reading rate of accelerated sidetone transmission times at four sound pressure levels were in vestigated (49). fie concluded that speakers read faster- under the condition of accelerated side rone than they do under the normal corid it ion of sidetone. i" ci 1,1'J O 3 X h CGI; U UC 1 0 G ci i i t X O t t r i l t ' I ; t 'V iii.C n V V cu o O t ** sicjiico to c x p iozc cnc- disc.uios.ncc ox limc co 1 cy , vjix.n pcti— ticular ref ere nee to the shape s of the curves and the location, of peak disturban.ee in articular ion, duration, intensity, and frequency (2c-). he concluded that delayed sidetone re suited in various types of speech disturbances, a rn o n y w n r c n v i e re i n c r e a s e o n u m u e r o r a r t i c u 1 a s o r y e r r or s , longer duration, greater sound pressure, and higher funda mental frequency. Disturbances of articulation and dura tion were interpreted as direct effects, chose of sound pressure and frequency as indirect effects. A correct word rate was proposed as a single, inverse measure of disturb ance that combines both direct effects of delayed sidetone. In a recent paper, Butler and Galloway reported the re suits of two experiments, employing a total of 338 normally hearing subjects (24). The rate of presenting reading material, the intensity, and length of delay of speech feedback served as independent variables. heading matter consisted of pairs of digits. A linear relationship was found between performance on the sidetone task and intensity of the delayed signal. These authors found no evidence of the influence of delayed sidetone of the lowest intensity level (20 db 3L) based on a loudness reference of the speech detection threshold. Fairbanks and Guttman conducted an experiment in vestigating the nature of the disturbance of articulation, using sixteen normally hearing subjects (29). These sub jects read the same prose passage five times. The rime delays of amplified (not described) delayed sidetone dif fer O ' q at e a c 11 r e a o i r. g , t h e v a x u c . s o ting t, 0,1, o, u, 0»A , and 0.8 seconds. The general effect was increase in toral reading irme and ois luroapxt wst maximal wnen '-he delay was 0.2 seconds. They concluded that delayed sidetone not only induces articulatory disturbances, but selectively varies the number of disturbances of certain types in relation to the specific interval of delay. They described the articulatory disturbances and noted that a high incid ence of additions 'was the most distinctive characteristic of the peak disturbance and about 70 per cent of the addi tions were repetitive. An interesting experiment recently conducted by Brungard combined the use of the galvanic skin response and dst (62). Skin resistance changes appearing as uncon ditioned responses to delayed sidetone were measured during the experimental employment of the delayed sidetone 20 application with fifty normally hearing subjects. These subjects cere divided into five groups undergoing five sensation levels of delayed sidetone; oO, 60, 40, 20, and 0 cb with reference to spondee threshold. The experimenter obtained the following results; (1) the variation of the response latency to the sidetone dupc-ared to be. strongly related to sidetone level as high. levels of sidetone p r o duced highly consistent variations in skin resistance; (2) analysis of the data seemed to indicate the possibility of me asurabit skin resistance changes in response to sidc- tone levels as low as 20 db; (3) judgments of the graphic records and latency measures resulted in highly accurate judgments as to the level of sidetone employed with each tO /U t-* 4 Slack conducted a study in order to discover whether speakers recovered from the effects of delayed sidetone in terms of reading rate and sound pressure within 160 sec onds artcr an exposure to delayed feedback during the read ing of 60 syllables (22). he used fifty-six normally hear ing cadets reading 10 lists of five syllable phrases. Signal delay was 0.30 second. In this work he confirmed his conclusion that the primary effect of delayed sidetone is temporal, which is in disagreement with 'fairbanksr s statement that articulatory disturbance is the primary e f f e c t. Adaptation to dst Atkinsonf in studying adaptation to delayed side tone, conducted an experiment using twenty normally hearing males (lo ). He charted duration and sound pressure level of short phrases over a long period in attempting to es tablish tentative norms for adaptation rates of SPL and duration during dst- .it concluded that no adaptation oc curred during the experiment in either StL or duration of speech. He indicated at that time that a longer reading time mi pint show adaptation and that this study did not rule out adaptation in other areas: i.e., perspiring palms, breath control, quality of speech, repetitions, or mis- pronounciations, He stated that the same could be said for other speaking or reading situations, other timing methods, or other sidetone levels. In a .Later experiment, published with the same title as the previous study, Tiffany and Hanley used twenty normally hearing males and presented ds1 at 30 db sensation level (SL) (bo), The material was a 4b~word passage read twelve consecutive times on one occasion and twelve con secutive times one week later. lie a sure s of reading time and reading fluency, and related measures of speaking ability were studied. There was no statistically signifi cant adaptation to reading in twelve feedback readings, nor was there adaptation from week to week. They concluded tha under the conditions of their study, readers cannot learn to overcome the effects of dst. In 430 readings, only three were faster than average normal reading time. In every case, the average dst reading time was longer than the average normal reading time. pe1ayed sidetone as a psychometric device Although the initial interest in the dst phenomenon centered on its audiometric use, other professional inter est has developed. A number of experimenters have shown interest in its use as a osychometrIc device. hpilka in an experiment attempted to determine wnether or net the variations in speech control under dst could be accounted for by personality factors (hi). Ac conducted what he termed an initial exploration and used data obtained from a battery of psychological tests and from four voice variaole measures. he correlated these scores and con cluded that vocal intensity variation under dst appears to be most closely related eo personality functioning; that increase in vocal Intensity variation under dst appears to be positively related to inadequacy and instability of the self-conceptual system and to paranoid behavioral tenden- cies; and that decreases in vocal intensity variation under dst appear to be significantly related to schizoid and socially isolating modes of behavior. Pronko and Leith in studying dst as psychological stress, devised an experiment using sixty subjects, wherein 23 they investigated the problem of whether or not subjects, required to perform a rigorously specific series of manual operations in a situation involving sudden, experimentally- induced stress, would demonstrate differential effects in behavior in three groups: (1) a sink-or-swim group which was parallel with real-life situations, such as air raids, etc.; (2) a p1anted leader group whcroin some member of the group rises to the occasion; and (3) a pre-practice situation, comparable to fire drills, etc.(50), Although there were differences among the groups regarding manual dexterity, it was concluded that the stress on speech behavior was approxirnately equal for the groups. Boyer investigated the effects of delayed sidetone stress with particular reference to the influence of the message spoken (61),, He concluded that subjects are less fluent under dst; that speech breakdown under dst applies to both male and female subjects as 'well as for pleasant, unpl easanc and n eutral content; that non-einotional speech content is spoken with greater fluency than emotional speech content under dst and not under it; and finally, that there was a tendency for male and female subjects to demonstrate a greater speech breakdown in fluency upon the introduction of a stress condition when reading pleasant sentences than when reading either neutral or unpleasant sentence s. 24 Dst and ma 1 ingex1 ing A number of delayed sidetone research reports have been concer ned with the application of the phenomenon ir. audiometx ic to suing in case s involving malingering. Among the early work on the consideration of this technique for clinical use. .\zzi' s application of dst as a modern version of the Lombard test, should oe noted (19). Using an ampli fied (not described) delay between 9.In and 0 . 2 0 se cond, he notec s. jc- c ta cu 1 a r srucre r rng , a; i rricrea s e in ri~ire nsrty oi rhe vorce , ano. a s a a c 2 e nr fig r n tne soccc. oi urrerar.ee . . iG r e c i 1 r z s . c i ear i s i . c . . . v : r r c r £ ■ 11 c y o i i n e l ■ _ cm i r s a1 . . . n c a s r - o i rnalingering. ferming his work "a preliminary ya.mzg 1 1 ne escribed rhe application or the "delayed voice" technique, in m e r orlovmraj manner; r\ C t t a X C X i ; 1 9 f r o m t h e 0 o i i i I o 11 a h a T , . ' Ar i i n d i v i d u a 1 c a n e x e r t a n ga r C 0 fit r o l 0 n * i x e OV! i i v .; 1' 0 C i o u n c i a t i o n , X c com e s r*' O r J ' h e c o rICl u s i o n t h a " C ci ny a X O U d i r ~ - re i n t l o d u c eel s u e h d c o n T 0 - O J _ ',9 1 ■ !! 1G id t h c c a r j 3 3 OU C ici c.a U 3 t s rnor e 01 l e s s .1n w o r " u a I i t d t ] t c x d " CiOii 0 I LC i e a I o fi 0 U f. 1. C i X X C i i \ } w h i c h o 0 e s i i\J L Ii Ci : a r i r i t h C c a a e o I a e 0 a l l y ci C ci X e a r . ( i v : 3 3 4 ) T d _ i. i ." d r .v a ■ t ' y iU l i 1 . C - J fid VC a i s c u o S i. C i a h i S a s..;c c <_ o f ti.st m malingerincg in much of their published work. The a series published by these authox e inciuoed a discussi.on of the roblem (or). ! heir aim i, t the experiment wa c to inve sr rga r e r ne p i o s s ioi 1 r t y o i u s - r ng the r e . su 1 s s r 11 c C ' n— structing a test foe the detection of bilateral auditory malingering and/or psychogenic deafness. They presented a lOO-v.’ord passage from Li.obinson Crusoe to thirty speech 25 students at 35, 55 and 75 db presentation levels. They concluded in this early paper that "it appears that reading rate is a positive function of the intensity of the delayed sidetone." In a later paper, these authors treated the same subject at greater length (35). They pointed out that the delayed sidetone test for malingering has the advantage of not appearing to be a hearing test at all, that there are individual differences in response to the disturbing effect of the sidetone and that the effect on speech is ordinarily of such an obvious nature that even the most naive or sleep- tical listeners cannot fail to detect it instantly. They also referred to the previous limitation in experimentation wherein studies of dst as a non-organic hearing test have employed normally hearing subjects who were carefully instructed to feign deafness. Gloria, in a paper devoted to the problems con nected with the management of cases of malingering, referred to the dst test and its obvious application to non-organic hearing losses in the following manner: This "delayed speech feedback" test is one of the few tests by which we are able to break into a physio logical "feedback circuit." If you will remember, I have stated that in order to objectively prove malin gering we must have a test which will differentiate malingering from psychogenic overlay. When the speech feedback test came to my attention I regarded it as a possible technique which would do just that. (34:815) 26 Dst research program in the Los Angeles V. A, AudllXogy Clinic Because of the peculiar problems related to the man agement of the examinations of disability compensation audiometric evaluations, it has become necessary in Clinics performing this service, such as the V. A. Audiology Clinic in Los Angeles, to seek more objective methods for deter mining organic threshold values, V/ith this objective in mind, a research program using delayed sidetone has re sulted in the publication, or acceptance for publication of a number of pape r s , The first experiment was designed to assess the relative effectiveness of three modes of delayed sidetone ( 6 8 ), These three modes involved the following presenta tions: bilateral, unilateral, and unilateral with contra lateral masking, The subject group was composed of one- hundred sixty normally hearing adults, reading a passage which contained five hundred syllables of expository prose, Results indicated that the bilateral mode of presentation is very effective, and should be used only when it is not necessary to test ears separately; that the unilateral mode without contralateral masking is the least effective, and should not be used clinically; and finally, that the uni lateral mode of presentation with contralateral masking is as effective as the bilateral mode, and can be used to test ears separately. 27 Following this first paper, an experiment was con ducted which resulted in the development of a clinical test for detecting unilateral functional deafness (31), Seventy veterans with medically diagnosed unilateral hear ing losses were used as the experimental group. No control group was employed in this experiment, which demonstrated that it was possible, using this technique, to detect non- organic elements in feigned unilateral hearing losses and that the clinical utilization of this technique was feas ible in standard audiology clinics. Certain problems arose following this publication, including the question of possible adaptation due to the length of the reading passage, which in the original experiment had been five huncred syllables. Also, it was believed imperative that more information be collected regarding normally hearing subjects under improved test conditions, and finally, that the relationship of unimpeded oral reading time to the im peded time under dst needed further study. Another problem which had become apparent in the clinical application of delayed sidetone 'was that of the effect produced by the introduction of a masking noise to one ear. It was noted early that a Lombard effect was taking place. The intensity of speech varied during this effect, and the question of whether or not this also had an effect in prolonging oral, reading was considered. If such double effect on reading time was operating, some method 28 would have had to be worked out to account for the separate components due to each. Therefore, an experiment was de vised using 1 2 0 normally hearing veterans in three groups, one undergoing unilateral masking noise, another undergoing bilateral masking noise, and a third with no masking noise (59). All three groups read a passage composed of five hundred syllables of prose. The presentation level of the masking noise was 80 db Sensation Level (SL), It was demonstrated that the obtained reading times for the three groups were not significantly different. It was concluded that, in she case of normally hearing individuals, auditory masking at sensation levels not exceeding 80 db does not produce clinically measurable alterations in elapsed oral reading time in spite of the fact that vocal loudness level, i.e., the Lombard effect, was noted. let this point in the clinic research program, the question of the extent of time changes in oral .reading times which could be used to detect or infer organic thresholds -was considered. It had beer, observed in clin ical application of cist, as well as having been described in the literature, that there was considerable variability in oral reading rate, For use as a base for prediction in dst, it was felt that more knowledge was needed regarding this problem of the variability in the rate of sustained oral reading without the application of delayed sidetone, A single group of sixty subjects was used, A reading 29 passage composed of 2 , 0 0 0 syllables of running discourse was employed. Each subject read the entire passage with out interruption while wearing headphones in an acousti cally isolated room, duplicating the conditions in dst testing. An analysis of variance indicated non-signifi cance and that prolongation of the oral reading task was not a source of variation in oral reading rate (32). Because of the fact that much dst testing involves lengthy test sessions, a further problem in this area be came evident„ Previous adaptation studies had been limited to the reading of short phrases and passages. It was therefore determined to investigate the extent ox adapta tion to sustained delayed sidetone presentation under one condition of signal delay and intensity within conditions duplicating clinical application of dst (60). A single group of sixty normally hearing subjects was used. As in the previous study, a passage comprised of 2 , 0 0 0 syllables was employed, divided into ten reading sections. Each subject read the entire passage while undergoing a bilateral dst presentation level of 60 db Sensation Level (SL). Each of the ten 2 0 0-syllable sections was measured for oral reading rate. An overall, analysis of variance indicated that there was among the ten reading times a statistically significant difference beyond the one per cent level of confidence. fiext, differences between individual condition means were tested and indicated that all of the condition 30 means, except for the first and second, were significantly different beyond the one per cent level of confidence. It was concluded that a significant degree of adaptation under a single condition of signal intensity and delay does occur after the reading of 400 syllables of prose. This was taken to mean that as many as 400 syllables of prose can be read in the oresence of delayed sidetone before any lessening of the speech-interfering effects will occur. The Masking of Speech The effect called masking occurs when any sound impressed upon the ear reduces the ability of the ear to sense other sounds (4; 153), V.'ever described it as primar ily a unilateral phenomenon, the effects depending upon the presentation of the tones to the same ear (17:387). He suggested that bilateral masking is a form of unilateral masking, which appears only by conduction through the head. Hirsh stated that masking is a kind of exception to our ability to analyze out of a complex of sounds, the one to which we wish to attend (6:154). It is the opposite of analysis and represents the inability of the auditory mechanism to separate the stimulation into components and to discriminate between the presence and the absence of one of them (13:1005). In clinical use, the term masking ordinarily refers to the introduction of a sound to an ear in order to 31 "block out" that ear while the other ear is being tested. One stimulus used fox clinical masking is a complex tone of saw-tooth variety. Very few experimental data have been collected for this type of masking noise, although it has been generally recognized that it is effective in masking speech because of the emphasis of low frequencies (6:173). Hirsh stated that we measure the masking of speech in terms of a shift in threshold, as well as measuring the change in the articulation score at a particular level (6:170). Miller described the masking of speech as the shift in threshold caused by the introduction of an interfering sound (8:62), As noise is introduced as the masking stimulus, the threshold of detectability is little affected but, at higher levels, this threshold increases by the same number of decibels chat tiie intensity of the masking noise is i11cr easoci. i ne ozg i i c i 1 io n o xsc ra c_lo iig c 1 5^ar y c or 1 no detection of speech is constant at high noise levels and the speech is detectable so long as it is not greater than 17 db less intense than the noise. In his monograph on the effects of noise on man, Kryter stated that the concept of critical band width, or that amount of energy in a narrow noise spectrum equal to the energy of a pure tone in the middle of that band, probably can be applied to the masking of speech in the same way it is to the masking of tones (74:66), Primarily a review of the literature throughout the entire field of 3 2 noise, particularly as it relates to the deleterious ef fects on man, this monograph covers such significant areas as amplitude distortion and its control as a technique for improving the intelligibility of speech in the pres ence of masking noise, monaural versus binaural listening as factors .influencing the masking of speech by white noise, interaural phase relations and the intelligibility of speech in noise, and reverberation time as an indirect measure of noise due to reverberation. Bekesy, in a paper on the structure- of the middle ear, stated that certain physical considerations of the middle ear increase the sensitivity of the ear to sounds coming from outside and at the same time decrease or mask its sensitivity to sounds produced by the organism itself. He also stated that the middle ear is so adjusted as to minimize noise pick-up from the speaker’s body during talking, vibrations from the vocal cords being distributed over the whole body (2 0 ). In discussing masking noise and delayed sidetone, Hewby stated that delayed sidetone can serve as a check for binaural or monaural functional loss and that when the sidetone is directed to only one car, the other ear should be rna sked (9:166 ). One of the most useful clinical tests using the masking of speech is the Doe.rfler-Stewart test, in stand ard use in the Audiology Clinic (25). This test examines 33 a subject’s ability to respond to spondee words in the presence of a complex masking noise ox the saw-tooth type. The theory of the test is that, if a patient has a non- organic loss, the masking noise will interfere with his judgment of the point at which he should no longer be able to hear the test material, often 'when the masking noise intensity is 1 0 1 0 1 0 db less than the spondee inten sity. This test is administered routinely in all cases of a medico-legal nature, such as insurance claims, veterans' compensation, and with military personnel. Lig’ ntf oot, Carhart and Gaeth explored the masking effects, using both pure-tone and speech, of white noise on ears with differont types and degrees of hearing loss (40). The hypothesis evaluated was that a noise of flat spectrum will produce the same amount of masking in an ear which is impaired - whether conductivelv or perceptively - as it will produce in an undamaged ear, provided that the intensity ox the noise is varied so that its effective level is the same for the two ears. Abnormal relationships obtained in the data for hypacusic subjects tended to in validate the hypothesis. Abnormalities revealed by the masking of subjects with perceptive disorders were gener ally more pronounced than were those revealed by the mask ing of subjects 'with conductive impairments. The results suggested that the concept ox the "critical band." as formulated by Fletcher and his colleagues, may have limited 34 applicability to the masking ox impaired ears, especially if the impairment is of the perceptive type, Miller and Licklider conducted an experiment using monosyllabic words at 90 db masked by interrupted random noise at four intensities (48). The noise-time fraction was 0.50. When the noise 'was interrupted more than 200 interruptions per second it was effectively continuous. Between 1 and 200 interruptions per second, it was pos sible to patch together the bits of speech heard between the bursts of noise and the masking effectiveness of the noises was rather 1ow. At very slow rates of interrup tion, whole '-words or groups of words are masked, and the perception is more nearly "all or none." Hawkins and elevens studied the monaural masking of pure tones and of continuous discourse by white noise and demonstrated that the masking curves for speech were simi lar to the curves for pure tones (38), At higher noise levels, the thresholds for speech are raised by approxi mately 1 0 db for each increment of 1 0 db in noise level. The curves relating the speech levels at the threshold of detectability and the threshold of intelligibility to the masking noise were approximately parallel. It was demon strated that at noise levels above threshold of 50 db and higher, the threshold of intelligibility is reached at a signai-to-noise ratio of - 8 db and the threshold of detec tability at a signal-to-noise ratio of -17 db. It was also demonstrated that for pure tones the average masking at 500, 1 ,0 0 0 , and 2 , 0 0 0 cos is almost ide ntical with the ave rage masking of speech measured by the average c 1ova tion of the t’ nrcshold of detectability arid the threshold of intelligibility. The experisunt supported the proposition that the. hearing loss for speech is closely correlated v; it S i iwie aver, age SL-ce rng .ion- . : . ae ostr, r , r:j . / , ano e, rOO c - . s i-jnen tnc snaps oi tns auuiogram i.s not coo lea. e yuior . i-ure tones have- been usco exper imentally to mask Truscott found thac low- f .a. rim ncy tones are: much rsoec ciis- ir: frequency, ' / . ' f i e e . ea s for weaker rorees approximately oOO cps is T.hc- most effocrlve frequency. As with the masking of one tone by another, they demonstrated that masking is C y if G c a X £ S X c-1_ ci [: f I aO O V C bill:. I lb ’ C 0 U C i 1 C y 0 1 b il C wlcl S r-l 1 1 .. K; b O P: tl • Their complex tones included rectangular ,uiscs and square waves. being composed of many harmonics, these complex waves were demonstrated to mask the e nt ire range of speech frequencies at lower intensities than go pure tones; how ever, at higher frequencies, both pure and complex tones were demonstrated to oe equally ineffective for masking specch. iigan reported an experiment which demonstrated that although a sufficiently intense noise in one ear will mask 36 speech heard in the contralateral ear, a weaker noise has the opposite effect; it enhances the loudness of speech heard in the other ear (26), A change in localization of the speech was also reported, being localized nearer to the center of the head when noise was introduced into the opposite ear. The author suggested two possibilities for this occurrence: the noise has an effect on the muscles of the contralateral middle ear, thus presumably increasing the physical in of the speech received at the inner ear, and this effect is also due to the similarity between the temporal a/rd frequency characteristics of thermal noise and speech, so that in the discrimination of loudness, the listener cannot distinguish between the loudness of one component as against the other component. Piiler masked speech v/ith narrow bands of noise by inserting highly discriminative filters into the noise channel to provide eight adjacent pass bands (47). The narrow bands of noise were then mixed with the speech, and articulation tests were run, A wide band masking noise demonstrated the most effective masking of speech. At low noise levels, the high-frequency bands were more effective than bands below 1 , 0 0 0 cps and, at high noise levels, the low frequency bands were more effective. He concluded that low frequency noise can, if intense enough, mask the entire speech range, Licklider demonstrated that the phase relations of 37 speech and noise at the two ears can affect articulation scores obtained at a giver, speech-to-noise ratio (44). When either the speech waves or the noise waves at the two ears are 180 degrees out of phase, articulation scores differ from those obtained, when they are in phase, indicating that masking is not a wholly peripheral process, Hg an and Wiener investigated the intelligibility of bands of speech in two spectra of masking noise (27). In one group of experiments the speech was filtered before mixing with noise and in the other group both the speech and noise were passed through the same filter. They con cluded that the articulation score is primarily a function of the speoch-to-noise ratio suitably averaged over the pass band of the system and that a noise component of a given frequency masks most effectively a speech component of the same frequency. They stated also that frequency components of the noise lying outside the pass band of the system will also contribute to the masking of the speech, this "spread of masking" being most noticeable for low- frequency components of the noise. French and Steinberg, in a paper concerned primarily with the articulation index, discussed the Interband mask ing of speech, or speech in one frequency .region masking the speech sounds in other frequency regions (30). They were concerned only with the interband masking effect on bands of higher frequency but concluded that lower bands 38 might be masked by adjacent higher frequency bands. Bolt and MacDonald developed a general statistical theory for the masking effect of reverberation on the intelligibility of words (23). Speech was considered a series of discrete pulses distributed statistically over a 30 db range in sound pressure level in a given frequency band. An articulation index was calculated as a function of reverberation time, using preliminary values of speech pulse lengths and spacings obtained from Visible Speech spectrograms (and considering sequentially the way in which various sections of a statistical pulse are masked by sec tions of previous pulses). CHAPTER III THE EXPERIMENT This chapter is devoted to a description of the design, the subjects who participated, the selection and use of materials, and the procedures employed in conduct ing the experiment. Experimental Design In order to test the hypothesis that a difference exists in elapsed oral reading times of selected passages between normally hearing and unila terally deafened subjects under the application of dichotic delayed sidetone and masking noise, a design was constructed whereby each sub ject had each ear tested independently in two separate experimental conditions. The experimental stimuli were noise and delayed sidetone, as well as the prose reading passage. These independent variables, as well as the delay time of 0.192 second, were kept constant so that each of the two ears of both groups was tested in the same manner (Experimental I . and Experimental II). In addition, it was hypothesized that there should be a difference between the pre-dst reading times and the delayed sidetone reading times. In order to investigate this hypothesis, the first 39 40 experimental condition (Unimpeded I) was constituted using the same type and length of reading material which was em ployed in the dst. conditions. next, the hypothesis that there is an effect on reading following dst was investi gated by setting up the fourth experimental condition (Unimpeded II) which was similar to the pre-dst condition. h/CPHiilMEI'jiAL DhSIGt: Subjects: normally hearing Unimpeded Experimental I Experimental II Unimoeded II 1 2 3 « 38 39 40 Unilater ally Deaf e ned 1 2 3 • • 38 39 40 Eighty subjects were used, divided equally into two groups. The population was composed exclusively of male veterans and included two equal groups, one of normally 41 hearing subjects and one of organically deafened unilateral cases. All subjects received the dichotic experimental stimuli in the same manner, read the same selected prose passages, and environmental conditions were controlled in similar manner. The dependent variables were the elapsed oral reading rimes of the subjects and the pathological ears of the organically deafened unilateral group. In order to avoid any bias due to any order effects, counterbalancing was employed. In the case of the normally hearing subjects, this consisted of the selection of the right oar for testing first with dst, followed by testing of the left ear; the next subject was res led with d st first to the left ear, etc. With the unilaterally deafened group, the counterbalancing was set up with dst being pre scarce d irrst co ino normally nearmg ear, a no reversed; the following subject was then tested with dst first to the pathological ear and reversed. It was decided that the groups would be further sub-divided into smaller groups of twenty subjects each for statistical treatment, to deter mine whether ox not differences existed according to which ear was tested first, Subj ects Subjects were selected from the routine flow of clinical cases scheduled for examination in the Audiology and Speech Correction Clinic of the Veterans Administration 42 Regional Office, Los Angeles. These cases are scheduled for compensation examinations or for treatment purposes, which consists of nearing aid selection and issuance and aural rehabilitation classes. Mo attempt was made to con trol the flow of these cases in order that the three major types of unilateral hearing losses— conductive, perceptive, and mixed— would be included in the study. The entire population consisted of eighty male veterans, whose ages ranged between twenty-one and sixty- eight years, subdivided equally into two categories as foilow s: The control group Forty normally hearing veterans were selected on the basis of an initial screening of case file material, set up to exclude any neuro-psychiatric, speech, language, or visual difficulty. The hearing acuity selection cri teria for each ear consisted of a pure tone average in the speech range of 1 0 db with no single frequency from 500 to 2 , 0 0 0 cps showing less acuity than 1 0 db, and with a Speech Reception Threshold of 10 db or better. In addi tion, no subject was included whose Phonetically Balanced (PB) test score fell below 96 per cent. The experimenta 1 group Forty unilaterally deafened veterans were selected for the experimental group. Each subject who was selected 43 demonstrated hearing acuity within the normal range within the same limitations established for the control group for the better ear, In addition, the organically deafened ear could be no closer to the normal ear than 30 db for both Speech Reception Threshold and pure tone averages throughout the speech range of 000 to 2,000 cps. In order to rule out the possible existence of any non-organic ele ment in these cases, the battery of standard Audiology Clinic tests for unilateral deafness was administered including the 3tengex (03), the Doerfler-Stewart where indicated (2b), the Shifting Voice test (9:164), and the Weber test (9:61). Finally, a medical diagnosis of organic deafness was made in the Ear, dose, and Throat Clinic after thorough otological examination. do attempt was made to categorize the type of hearing loss according to diagnosis. (See Appendix A. ) materials The materials consisted of screening and experimen tal reading passages, masking noise, electronic equipment, and a sound-treated two-room test suite. Oral reading material Early research workers in dst used short phrases without giving particular reason. One difficulty in using short phrases is that the timed results tend to be similar, thus obscuring the dst effect. It has been noted that 44 phrases have an advantage over separate words, and that sentences have a marked advantage over separate words or phrases, as reported by Stinchfield (15:241). Hirsh, howeverj stated that the most valid sample of English speech for testing communication ability is a whole para graph or several paragraphs of continuous discourse and that the use of such continuous passages employs a kind of method of adjustment (6:132). In selecting the level of reading difficulty to be used for the study, it was necessary to discover what per centage of American adults completed an educational level sufficiently low enough to enable the experimentor to in clude most veterans and yet not low enough that the reading material would be too easy, dull, or uninteresting. Flesch stated that the 1950 census figures show that 91 per cent of United States adults completed the fifth grade (3:44). For this reason, the level of fifth grade reading ability was selected for this study. In addition, this level is reasonably stable and beyond the laborious, difficult stage of reading which is passed by some children, according to Stinchfield, in the second grade (15:241). Most, however, do not master the technique sufficiently to road easily until they reach the third grade. However, once the mas tery is attained, the rate remains relatively constant. A prose passage selected from a fifth grade reading text currently in use in the Los Angeles City School 45 System was employed to elicit the oral reading responses (1), In order to insure uniform .reading of the text, the passage was edited to eliminate headlines, dialogue and figures. This editing produced a continuous prose pas sage which consisted of sixteen hundred syllables. This passage was divided into four equal sections of four hun dred syllables each, (See Appendix D.) An analysis of the reading passage was made in order to determine its reading ease according to the Flesch formula (3:5), There were 8 ,99 words per sentence and an average of 137 syllables per hundred words fur the total passage. This resulted in a reading ease score of 82, which fails into the "Easy1 1 category. The reading material was typed in triple space with two hundred syllables per single page, In order to protect this material, pages were encased in two transparent plas tic sheets, which 'were secured with scotch tape. Holes were punched on one side of the sheet and each sheet was put into a hard-backed loose-loaf folder, When the folder was opened, page one was on the left side and page two was on the right side, The same arrangement was made for all eight pages. The final sentence at the bottom of page two, four, six and eight was complete, so that no time was spent in turning the page, In this manner each four-hundred- syllable passage could be read without interruption. Each passage was composed of four hundred syllables. 46 Previous clinical research lias demonstrated that adaptation occurs after the reading of lour hundred syllabic & '.vinenever one presentation level is constantly maintained (60). Thus, the length of each passage was set so that no adaptation would occur during its reading. 1 he ( f l ea suroi c 1 a sco rc^ac j .r. iip crme The study of elapsed reading time was decided upon. I t i s c o n s i d e r e d a t t h i s t i m e t o be s h e moor o b j e c t i v e c l i n i c a l m e a s u r e . . .cv.'by s t a t e d c h a r t h e one v o i c e c h a n g e w h i c h c a n be m e a s u r e d c u a n t l b a r i v L l y i n t h e d e l a y e d s i d e - t o n e t e s c i s csura c r o n ( v ; l o r ). ,i u t a r r _ a r t i c i e on a o a o t a— t i o n , T i f f a n y a n d h a i d e - y c o n c l u d e d t h a t , a l t h o u g h . r e a d e r s l e a r n e d t o a v o i d r e p e t i t i o n s , o m i s s i o n s a n d o t h e r s p e e c h ci i. 1 +' ■ rations from one series of delayed side tone testing to another one week later, they did not learn to overcome the duration effect (uo:171). The possibility or controlling the individual sub ject’s reading rate was considered initially. however, it was discovered that little research has beer, conducted to determine the average rate or oral reading. Jones, in dis cussing variation in rate of speaking, quoted fields and Bender as stating that rate of speaking, like other charac teristics of voice and speech, varies with the individual and the subject matter and that no definite figure can be imposed on all; also, an average rate of 135 to 176 words 47 per minute fox ordinary material is recommended by differ ent authorities (65:19). Goodman-Malamuth stated that evaluations of speaking rates, in the past, have been handled on an arbitrary ox subjective basis (63:5). Stinchfield described a study by Huey which demon strated that reading rate ranged from 2.5 to 9.8 words per second. She also referred to work by Dearborn showing that rapid readers read three times faster than slow readers (15:240). She also discussed the work of Book at the University of Indiana, who found great individual differences in the reading abilities of students (15:249). In her chapter on oral and silent reading. Stinchfield presented a table of scores in oral reading tests at mt. Holyoke College showing a range of 58-297 words per minute among 1883 freshman subjects, Kelly and Steer, in considering elements of rate and judgment cf rate, concluded that extemporaneous speech is extremely variable in rate, ranging from 125 to 328 words per minute on the average (40:226), In describing work done by other experimenters, they continued: Cotton used the syllable as his unit of rate and concluded that . . , rate varied from 50-450 words per minute. , . . Franke has indicated that the correlation between over-all rate and ratings by judges is very high. . . . She also reports the correlation between the over-all rate and judgment to be slightly higher than the phrase rate and judgment. . . . Fairbanks and Hoaglin have also indicated a wide range in rate < . . being 136-320 words per minute. In a recent work, Pierce and David in analyzing 48 this problem, stated that reading aloud involves a very primitive form of thinking (11:192). They stated that reading rate is not limited by the time taken to utter words; familiarity with the words is one factor, and mental limitation is another (11:193). Jones, after dealing with this problem of trying to establish norms for reading rate, recommended that a study of twenty or more contemporary speakers, treating variety of rate, would be a welcome addition to the re search of the field (6b:6 8 ). Because of the lack of agreement regarding average rate of reading, no attempt was made to control or alter experimentally the individual elapsed reading times for the four-’ nundred-syllable passages. Determination of reading ability Prior to administration of test material used in the experiment, subjects were required to read aloud Gray?s Oral Reading Test for determining fifth grade read ing ability (7b). This was typed on one side of a four- by-six inch white card encased in plastic. (See Appendix C. ) Subjects v;ere also required to read aloud from the reverse side of the card, material instructing them to read as clearly and distinctly as possible. This require ment enabled the experimenter to screen subjects rapidly. In the instructions for scoring Gray4s Oral Reading 4 9 Test, directions are given for scoring individual reading performances. Seven errors per paragraph are permitted before a subject is stopped, In addition; there is a com plicated procedure for accounting for the time to read a given paragraph ar.d for evaluating the reading performance of an entire class. Since each subject in this experiment was tested individually, an arbisrary choice of proficiency was mads, a 1 loving three errors. These included errors of omission, insertion or repetition as described in the "Directions for Giving Gray s Oral heading Test." Few sub- jeers rsil-SG this rear; moss- voo railed did so on the basis of language dirficulry, The dst prcsencacion level U: i isidexed important that the dst presenta tion level be high enough, without producing discomfort, to insure that a large percentage of cases would demonstrate speech break-down. Describing the clinical application or dst to a subject suspected of exaggerating a hearing loss, Hanley and Tiffany stated that "reading began to slow at the 40 db level and at the 60 cib level shoved typical marked symptoms of breakdown . . . there was a marked slow ing of rate" (3b;GOO), Hirsh, in his chapter on the intel ligibility of speech, shows that ordinary speech ranges from 55, 70 to 85 decibels SPL for faint, average and loud speech respectively (6:150). Sixty db was selected as the dst presentation level to insure break-down and to fall within the range of ordinary speech. Choice of masking noise Continuous masking was chosen because of its general effectiveness (13:1049). Complex masking was chosen in preference to white noise because ox its greater effec tiveness in masking speech. (See Appendix E,) Hiller and Licklider, in discussing the masking of speech by nar row rands ox noise t seated that at high noise levels, the low frequency bawds n re more effective. They also con cluded th ere ioiv i xocjU(jiicy nod-Stc Coin -ncibk lIic tnt-Lirt spec c,h range if it is intense enough (13:1049). Hirsh agreed with this conclusion when he staled that the dependence of the masking of speech, by both complex tones and noise, on frequency indicates that the typical mixtures ox noises that are found in factories, offices and airplanes, with the usual emphasis of low frequencies, arc particularly well adapted to give a maximum amount of masking of speech (6:173). Masking noise presentation level A problem similar' to the relationship between the dst presentation level (60 db 5L) and the presentation level of the masking noise in the present study, was ex pressed by Licklider and Miller in their discussion of masking and noise intensity. They stated that the relation 51 between masking and noise intensity is often expressed by saying that the spoech-to-noi.se ratio. or d/k, at the masked threshold is constant over a wide range of inten sities (13 ; 1 '049). For most noises encountered in practical situations, S/k should exceed 6 db for satisfactory communi cation, although the presence of speech is dote ctable for 5/k as low as -Id do. If the speech is d is torted, higher values of 8 /’ k may be necessary. ”ith the above considers- t x o 11 s x n i n i i; o , e s o e c x a 1 X y e i \ e o c . x ■ . ■ c — 1 O Cl O -.J / > , Ci X V. V t i 'J 1 i i * o iV X i i ' ' . i V -i. than trie dst was thought xo be needed in clue o : : x . sent cxpcr- lfilG lit* In arriving at Lho proper amount or maokiny v.'hich would serve, an attempt was mace to discover any recommen dations for proper levels of masking. Hirsh, in discussing the elimination of "cross-hearing" of tom. s in the clinical use. or ma s King , sxaxc.o max roe e x xmx nax xon ox contrala xcral stimuli, the over-ail 3HL of the masking noise must be about 3d qo , a nci wc c ouid x..c. ea ec ila x i\ox sc io aooux od ob . db and still be quite sure that it would not stait masking the tone presented to the corse oar, even if than car were also normal. Yiith this 80 db of noise, he continued, we could be sure of measuring, in the bad car, as much as bO db Hearing Loss before any unmasked signal would evoke a response from the good car. For Hearing Losses of greater than 8 0 db on the bad ear, the intensity of the masking tone in the good ear would have to be increased proportion ately until about 120 db is reached (6:176). Since the experimental group of unilaterally deafened subjects ranged from a minimum of 30 db difference in acuity when compared with the good ear to "cotally unmeasurable on clinical audiometric equipment, it was felt that a high noise level was necessary. In addition, there was the added unknown factor of the effect of the internal cross over of a self-generated auditory stimulus, such as found in the continuous discourse spoken by the test subject. The level of masking noise, in addition to masking out this effect, also had to cancel out the auditory radiation around the head as well as that transmitted by vibration through the head-bar.d of the car phones. Zanderman stated that tne nature and amount of mask ing noise to be used is still an indeterminate matter (b:127). rewoy agreed witn tins point oi view when he stated that although various systems of determining the proner re'vel oi masKing nave- oeen suggested, none has gained acceptance (9 :ul). After considering the various statements of the authorities in the field, and recognizing the lack of agreement regarding the proper level of masking to be used for eliminating a speech stimulus, and with considerations mentioned above taken into account, a level of 80 db SL was decided as necessary for the purposes of the present experiment. Equipment The electronic equipment used in the experiment consisted of a Serlandt tape recorder, model DRX1, oper ated at a speed of ' / ' h i inches per second, and employing a fixed delay time of 0. 192 second,, This tape recorder is permanently wired into an . ‘ -.Hi son Series 21 dual-channe1 audiometer ‘ which permits independent control and attenua tion of separately monitored stimuli through each channel, ’ • . ‘atoned TDH39 Telephonic earphor.es with wX 41AR cushions were used. ,\n Electro-Voice ,7.ode 1 oS0 microphone was used with a Turner "Third-hand" chest place; attached to this was a flexible goose-neck projection supporting the micro phone. The experimenter adjusted the microphone approxi mately six inches from the subject's mouth so chat the speech was directed across it. Standard clinical calibra tion procedures were routinely observed. Test room All testing was conducted in the same standard two-room acoustically isolated audiometric test suite in the Veterans Administration Regional Office, Los Angeles Audiology and Speech Correction Clinic. Lighting, subject positioning, ventilation and similar factors were the same for each test. Ambient noise level for the subject room as measured on a Soundscope Sound Level Meter and analyzer, Model A, and set on the Analyzer position, was 26 db in the range from 76-20,160 cps. Procedure s V/hen the subject's hearing had been tested and his medical files screened and he had been deemed acceptable for use in the experiment, he was taken into the patient room of the two-room acoustically isolated test suite for further screening. Screening procedure 1 i no suoj ect was given the card with Gray’s Oral Reading i e s t typed o n j . . ^ a i. ' — i asked to r e a d it aloud. Fol lowing a succe s sfu1 reading, he was asked to reverse the card and to read aloud the printed in st ruet i o n s. (3c e Appendix C. ) If accep " c e q i o r ^ L L * d ' / , l n 0 sU D J 0 0 0 VI 3, S then given the test material in a hard cover notebook and a separate single sheet of other fifth grade material encased in plastic. Ho was told that the signal would be the standard one by the experimenter of pointing a finger, which could be seen through the multiple windows between rooms. In addition, it was explained that the first sheet was simply used to adjust equipment settings. He was told that after three or four lines of reading material the experimenter would speak over the headphones instructing the subject to stop reading and to drop the single sheet onto the floor, at which point the test was ready to begin. 5b At the signal, the subject was instructed to begin reading at the top of page one and to continue to the bottom of page two without stopping, i.'.aterial was arranged in such a manner that no break would occur. The first half of the reading material was on the left hand side of the book and the second half was on the right side. Thus, p.o turning of the page was necessary during the reading of any phase of the ci.tire test. The subject was told that upon com- Prerrng page s t.wo, i our and six , ne was to stop anc rum around to awail the noxt signal to begin. The subject was the;; given the oppor tu!jity to ^ a a;;y eraea stons , w-nrch wer' c answe.eed rmm.ciatcry, anci headphones aricr microphone w ore tne 11 placed on me s u o jocr anc; scjusced prope.r 1 y. The experimenter returned to the test room and gave tne first signal to begin re aci m e , intensity settings on two VU meters,one on the tape recorder and the other on the other on the .-silicon Console were; set in standard clinical fashion in order to get zero peaks of the subject's speech. All dials were set to the lowest possible readings for attenuation, the oar to receive the dst first was selected from the audiornetric data and dst on channel one was switched to the proper position. idolse was set up on the selector switch for channel two and calibrated using the special calibration control on the console. Vi he n the peaks at zero were adjusted, the experimenter switched on the microphone and told the subject to stop reading and drop b6 the sheet onto the floor. Experiment a1 pr o c e d u r e The experimental procedure consisted of the reading of the separate four-hundred-syllable passages in four conditions: (1 ) no delayed sidetone nor masking noise, (2 ) delayed sidctone to one ear and masking noise to the contralateral ear, (°) delayed sidetone to the other ear and masking noise to the contralateral ear, and (4) no delayed sidctone nor masking noise. The signal, vns given to the subject to begin reading in the first condition. Using a stop-watch, trie experi menter followed the reading from a separate copy oi the reading passage while monitor ing the speaking or. both VU meters. At the end of page mo, notation was made of the elapsed time for the first condition. A rhree-minuto pause followed during which controls were adjusted to deliver oO db of cist (re : SAT of the better ear) to the selected ear and bO db (same reference level) of masking noise to the contralateral car. The signal was given to begin the experimental condition. At the end of page four, notation was made of the elapsed time for this second experimental condition. A three-minute pause followed during which the two stimuli at the same levels were switched to be presented to the opposite ears. The signal was given to begin, and at 57 the end of page six, notation was made of the elapsed time for this third experimental condition. Again there was a three minute pause, during which both channel attenuators were lowered to their limits. The signal was given and at the end of page eight, notation was made of the elapsed time for this fourth experimental con dition. The four conditions constituted the entire testing of each subject during the experiment. CHAPTER IV PRESENT ATI OK AND I NT EHP RETATIOH OF THE DATA During this experiment, elapsed reading times were measured and .recorded for each of the four experimental, test conditions previously described. These reading times obtained from this investigation were treated statistically in order to discover similarities and differences among conditions for two major groups: (1 ) normally hearing, and (2 ) unilaterally deafened. In addition, the unilaterally deafened group v;as further subdivided. Statistical Procedure The data obtained in this experiment were subjected to xhe statistical treatment, the Analysis of Variance. F-ratios and t-ratios were obtained (12:244; 2:177). 'then a number of groups and consequently a number of means are involved, F can be used to advantage, providing an over-all test of significance among the different means. If F meets the level of an adopted significance, we may then make specific comparisons with the t-test (2 :2 0 1 ). This experiment met the criteria set forth by Lind quist with regard to the necessary assumptions underlying the application of the F-test (7:73). 28 59 The level of significance adopted for this study was the five per cent level. This level was selected because of the wide variation among elapsed reading times observed throughout the experiment. Analysis and Interpretation of the Data The major interest in this experiment lay in the analysis of the foilowing three elements: (1 ) delayed sidetone effects, (2 ) unimpeded reading, and (3) possible adaptation during the presentation of dst. Minor interest centered on the study of the effectiveness of varying dichotic dst and noise presentation. Delayed sidetone effects Measures of central tendency and variability showing reading times for the total population as well as related data are presented in Table 1. Ref erenee to this table shows a similarity between conditions Unimpeded I and Unim peded II within both groups in mean times, as well as in the range, although dif ferences exist between groups. There is also a similarity between conditions Experimental I and Experimental II for the normal group, which is not as apparent for the unilaterally deafened group. Large numer ical time differences can be noted between dst and non-dst reading for the entire population. The entire population was analyzed to investigate whether or not there was a statistically significant 60 TABLE 1 GROUP READING TIMES IN SECONDS Groups U Mean Times 5D Range iiorrnal s Un. I 4 0 102.9+1.70 1 0 .6 +1 .2 0 8 6 . 2 - 130.8 ( 44 . 6 ) Ex. I 4 0 136.4+3.60 22.5+2, 54 100.4 - 199.5 ( 99.1) Ex. II 40 134.9+3.73 o n g +p 64 102,4 - 2 06 . 6 (104.2) Un. II 4 0 99.7+1.55 9 . 7+1 . 1 0 8 6 , 1 - 129.5 ( 43.4) U n i I a t e r a 1 c . Un. I 40 109.3+2.30 14 .7+1.oo 82. 3 - 141.7 ( 59.4) Ex . I 4 0 126 . 0+3 . oo ' 4 y ) G +9 59 85 . 9 - 2 1 0 . 6 (124 . 7 ) C v A • II 4 0 133.4+6,26 39. 1+4 , A V 91.3 - 286.7 (194.9) Un. II 4 0 106.7+9.21 13.8+1. 56 76.8 - 137.3 ( 60.5) difference in this entire combination of treatments for the normally hearing and unilaterally deafened groups. (see Table 2. ) An F-score of 22.20, significant beyond the one per cent level, was obtained through this procedure. In analyzing this result, consideration had to be given to the possibility of differences existing among the conditions as well as among groups. Because of the prolongation of elapsed reading times for both Experimental I and Experi mental II conditions for both groups, it seemed feasible that the statistically significant F- ratio described in this table was probably due to the difference between unimpeded reading times and delayed sidetone reading times, as well as to any possible differences between groups due to dst performance. TABLE 2 ANALYSIS OF VARIANCE OF THE ELAPSED ORAL READING TIMES OF THE TOTAL POPULATION UNDER FOUR TilEATmEiIT CONDITIONS Group s Compared Source of V aria t j. o i i Sum of 3 quares df Mean o qua r e F Ratio P Normally Hearing to Unilaterally Deaf ened Between Group s V: i t h i n Groups I oral 74 ,819.12 13 0,219.66 7 3i2 10,6 8 8 .44 4 8 i . 4 7 2 2 . 2 0 > 1 2 223,03 9.00 319 The two major groups wore analyzed independently under the four conditions. (See Table 3. ) An F-ratio of 47.27 was obtained for the normally hearing group under the four conditions. This result is significant beyond the one per cent level of confidence. In addition, reference to this same table indicates that the unilaterally deafened group treated independently under the four conditions pro duced an F-ratio of 14.87, and this result also was beyond the one per cent level of confidence. Since these- analyses of variance for the entire population and for the major groups, compared independently with the four conditions, resulted in .Levels of confidence beyond one per cent, it became necessary to subdivide further. 62 TABLE 3 SUMMARY OF THE ANALYSIS OF VARIANCE OF ELAPSED ORAL READING TIMES OF THE NORMALLY HEARING AMD UNILATERALLY DEAFENED GROJPS TREATED INDEPENDENTLY UNDER FOUR TREATMENTS Groups Source of Compared Variation N o r m a l l y Hearing j 4 Treatments; Unilaterally'j Deafened ! 4 Treatments I D G t VV G C H V.'ithin I ot a 1 BCT.wee r : V; ithin Total Sum of Squares df Me a n Square F Ra t i o P 46 1179.27 50,802_.63 ' • N 156 15.393.09 325.66 47. 27 >1% 96,9«1.90 159 28,44 2. 94 99,417.22 O 156 9;480.98 0 37.29 14.87 ' ■ ■ ) O X 127.860.19 159 In order to separate the unimpeded reading effects from the dst reading effects, the two groups of normally hearing and unilaterally deafened subjects were combined. (See Table 4.) An analysis of variance for these combined groups under Experimental I and Experimental II conditions TABLE 4 ANALYSIS OF VARIANCE OF THE ELAPSED ORAL READING TIMES OF THE COMBINED GROUPS Uf'DEK T REA i Pi r i■ITS EXPERIMl:NTAL I AND II Groups ■ G jourcg o i Variat ion - r run, o£ Square s df Mi o a 11 Square F Ra t i o P Combined Groups Treatments Exp. I & II 8 0 0 vv e e n 1/ ithin Total 3,168.18 124,477.50 127,645.68 3 .156 159 1 5 056. 06 797.93 1.3 Non- Sig. 63 resulted in un b-ratio of 1,3. This r- score was non-signif icant, indicating a similai ity of the two groups v;hen com bined in this manner for the conditions considered. Examination of the raw data collected for the unilat erally deafened group demonstrated that no case of dichotic pre sc n t a t i c n or no poorer car v;as no: to rhc n e t t c r eac . colon wd than the .eve: xo r.ir a . cat r 0.0 r,n or acr mare seatrstrcaj. compan ions oi tne ixoL-rirncntai 1 as t h; c. L !iiuh i l ; conditions I o r t h e p i o r s i r i i y i i■ u r r n g g : o u -- c o i so 1 1 1 e c : i t n e I .c u r . r 1 a c— eially deafened group, the- randomized reading times for the U n 1 1 a L 6 .. a 1 1 y G £ n ■ : 1 1 C £ ■ ■ - 0 U ! - cornume-d iI 1 L . O two s era rate ;rouo: i sole u. ) wne group is a column oi TO case i ■ n \ .. b) i r r Oli Al. if I: , ,'ITIi Thu Uhl .. p.- . ,CLv ;_J 1 i . i 1 r .. l-yi.--.i-. U y 1 ..-V f h. ./-iLilY"Dr. h:f i rea toe nt otai dst ( L. X . i L i G11 e r r a -I) o t a i c s t (i.x. I < T I I ) poorer : t . . hh.tTIO: .Z.J U . - J l .e a n i i 'lie . n i cc o nd' i - o . o of dst to tire better oar for both Lxnerimental I and Exper imental II conditions, as well as a column of all 40 cases of reading times obtained when delayed sidetone was pro- 64 senteci to the poorer ear. Table 5 presents the means for these two specially manipulated groups. Reference to Table 5 indicates that the mean times of 116.3 and 148.6 seconds show greater difference than was demonstrated between these conditions in Table 1, page 60. Y/hen these data, obtained from the unilaterally deafened group, were manipulated In the manner described above, it became possible to compare the two groups under all four conditions in the experirnent. This produced an JF-ratio of 10.32, which proved to be statistically signifi cant beyond the one per cent level, indicating the possi bility that at least one of the groups differed from the others. (See Table 6 .) TABLE 6 ANALYSIS Or 7ARIANCE Of i*OUR TREATMENTS: EXPERIMENTAL I AND II OF THE NORMALLY HEARING GROUP AND AnD PCORE COMBINED DSI 1IME3 10 R EAR OF THE UNILATER/ THE .ELY BETTER EAR DE A F EI 'iED GROU P Groups Source of Var iation Sum of S quare s df me a n S quare F Ratio P Normally He aring Exp. I &. II Unilaterally Deafened Dst--Better (40) Dst— Poorsr (40) Between V/ ithin 21,120.90 106,461.00 3 156 7,040.30 682.44 10.32 Total .127,681, 90 159 Next, the dst conditions, Experimental I and II, of 65 the normally hearing group were combined with delayed side tone reading times to the better ear of the entire unilat erally deafened group which had been specially manipulated. This statistical analysis resulted in an F-ratio of 2,92, which is non-significant. (See Table 7.) Thus, it was TABLE 7 ANALYSIS OF VARIANCE OF THREE GROUP TREATMENTS: EXPERIMENTAL I AND II OF THE NORMALLY HEARING GROUP AND COMBINED DST TIMES TO THE BETTER EAR OF THE UNILATERALLY DEAFENED GROUP T re a true nt s Source of V a r i a t i o n Sum of Square s df i.iG c i n Square F Ra t i o P Norma ily Hearing Exp. I d II Unilaterally 3etv;ee n V; it hin 4 ,7b7 .b4 95,111.o 0 ' z . 117 2,378/77 812.91 2. 92 Mon- sig. Deafened Ail Dst t o Better Ear (40 rates) T otai 9 9, eb y. 0 4 1 t'G J. J. > possible to demonstrate that the normally hearing group scores fox conditions Experimental I and Experimental II were similar to the group of 40 better ear delayed sidetone times of the pathological group. Having established the similarity described above, it was determined that the unilaterally deafened group should be further subdivided. Instead of combining all dst reading times to the better ear, which Included Experi mental i and Experimental II conditions, it was decided to 66 combine all reading times obtained when dichotic presenta tion was presented to the better ear first. This resulted in 20 cases for this sub-class. The same grouping was made for the 20 cases involving delayed sidetone reading times to the poorer ear first. For measures of central tendency and variability for each of these sub-classes, see Tabic 8. TAdLE o READI AG TIDES FOR THE SUB-DIVIDED Uni LA i L RaLLY DLaF ti'iED OROUP Treatment s mean i line ij s i . — j ij Ra no e e r r : ' S t Un. T 20 i 10. o4-o 72 10 . 242. Ex. I O (j i X 30. 9+5.57 . 3 +-r » Ex . II 20 I J . O .4+4 .2l— : • ib.6+2. Un. II 20 1 04. 7±3 • 17 13. 0+2.At S ' 1 , b ob« 6 146.3 ( 35,0 210,6 (i 06.3 169.4 ( 68.1 137.3 ( 51.7 roorer car Un. I Ex. I Ex. II Un. II 2u z. n 20 20 108.3+2.93 lib,2+3,I0 160. 34-9. 66 i Or.o+3.3 9 13.0+2.11 13.6+2.19 4 / i » j. + g * l o Z . 14.8+2,4U $ r i o u 1 c ing dst to the pooror car c2 o _ 136. 4 85. 9 - 154 . 0 12. 0 _ 286 . 2 76. 0 133 . 0 e ator dirte r f 0 the q rou tween the sa ,e c i it Xerence ( 54.1 the two sub-classes of the unilaterally deafened group wore combined and again mean times, standard deviations, and ranges were sot up preparatory to employment of the t-tests. Table 9 shows these measures, computed for the differences. 67 TABLE 9 DIFFERENCE IN READING TIMES FOR THE UNILATERALLY DEAFENED GROUP BETWEEN THE TWO CONDITIONS: DST TO THE BETTER EAR FIRST AND DST TO THE:. PGOHuR EaR FIRSI Treatment N Mean Times 0 D Range Dst_ Better Ear F ir st 20 20.9+ 2„96 12. 9+2. u9 6.1 - 39.6 ( 33.5) DSX Poorer Ear First 20 44.If 2.3 9 iO.lt 1. o9 13 . o - i32. 2 (118.6) In the delayed sidetone test referred to previously (31), a conclusion was drawn from the data in that expo ri me no recommending max. one teso oresontaeion sequence was superior to the other, when delayed sidetone- was presented first to the normal ear. This conclusion wa3 based on a small difference between the mean differences of sequences, which was 6.1 seconds. However, this material was not sub jected oo further statistical analysis. In the present study it was decided that such statistical analysis should be made concerning the difference of these differences between sub-classes. Table 10 presents a _t-rat io of 2,77, which is significant at the two per ceno level, and which indicates that there is a difference between sub-classes, and that the condition where delayed sidetone is presented to the better ear second is clearly superior for clinical 68 evaluation of the unilaterally deafened subjects because of greater time differences. TABLE 10 A STATISTICAL COMPARISON OF THE DIFFERENCE OF THE DIFFERENCES IN READING TIMES BETWEEN CONDITIONS EXPERIMENTAL I AND EXPERIMENTAL II CHEN DST IS PRESENTED TO THE BETTER EAR rlRST AND WHEN DST IS PRESHi TED TO THE POORER EAR FIRST Fur THE U'NILaTEFIALLY deafened group UnilateraIly Deafened 3l’OUi D< d c x x l r poorer I 1 . 1'; .c ; , L j , -L : _ A a l -j o Obta incd Level of i ignit rcance >Z j I n.e most imp or xanx sinote finomg ru xnc experiment was that there is no statisticalLy significant difference tween the too dst test phases of diehotic presentation of delayed sidetone and masking to a normally hearing group. The clear-cut nature of the findings obtained with respect to the comparison of the two groups in the several statis tical treatments demonstrated that there is a significant difference between unimpeded reading and delayed side tone- reading for the normally hearing group, and that among the unilaterally deafened group there was a significant differ ence among the unimpeded, the delayed sidetone to the poorer ear, and delayed sidetone to the better ear conditions. This finding of a difference between unimpeded and impeded reading rates is in agreement with previous research. Thus, 69 it was possible to state that findings are substantiated from earlier experimentation conducted in the Los Angeles Regional Office Audiology Clinic. These findings demon strated that a difference of 1U or more seconds in elapsed reading times is indicative of a hearing defecit of 30 db or greater between normal and pathological ears. The oppo site conclusion was also substantiated, that any difference of less than 10 seconds between test phases must be con sidered as indicating either .normal hearing or an asymmetry of less than 30 db extent. Thus, it can be stated that these groups do not come from a common population, relative to the dsi effect. V/hen dst Experimental I and II conditions were treated statistically and included both subject groups, with counterbalancing allowed to remain as originally planned, there was no significant difference between these experimental conditions for the combined groups. Then the counterbalancing was adjusted and the two dst experimental conditions for the normal group were compared with the adjusted unilateral groups, composed of all dst to the better car and ail dst to the poorer ear cases, there was a significant difference. When only three groups were com pared, Experimental I and II for the normals, and all dst to the better tar, no significant difference prevailed. It can be seen from these findings that such counterbalancing in the case of the unilateral group, where a difference in 70 acuity existed between ears, lessened the dst effect by equalizing the results for the pathological group between good and poor ears. By treating the pathological group as two sub-divided classes, it was possible to compare the effectiveness of the two methods of presenting unilateral delayed sidetone. For the sub-class having dst application to the poorer ear first, there was an increase in the prolongation of oral reading times among the three conditions: unimpeded, dst to the poorer ear, and ds 1 : to the better car. This resulted in a more effective time differer.ee between the two dst reading times pie case, than appeared in the sub-class, dst to the better car. V.'hen dsi is given to the bettor oar first, followed by dst to the poorer ear, the reading time increases, causing a snorter time cititronce Dexween ears, i he noare st t ime gr1 i crencc tor all cases of tn.e sub — c 1 ass , dst to the poorer ear first, -was 13.6 seconds, well beyond the critical 10 seconds limitation described earlier. Thus, the application to the allegedly deafened ear first in claims of unilateral deafness, is clearly superior to the reverse test method in terms of greater time difference. Unimpeded reading It has become increasingly apparent in the clinical setting that the use of unimpeded oral reading times as a basis for further testing using delayed sidetone is indi 71 cated. However, the question of when to obtain unimpeded oral reading times must be determined. '.Vith this end in view, an analysis of variance of Unimpeded I and II condi tions for both the total normally hearing group and the total unilaterally deafened group 'was computed. defer ence to Table 11 shows the F-ratio to be 3.93, which is statistically significant beyond the one per cent level of confidence. TABLb 11 analysis of variance of combiled readikg times OF TAEATMEhTS UNIMPEDED I AHD UEIMPbDhD II FOR THE UOrjViALLY HEARIHG AMD UAILATERALLY DEAFbiiED GROUPS Conditions Compared Source of Varia ti o n Sum of S auares t df Me a n S qua re F Ra t i o P U n. I Un. II Between A i t'n i n l ota 1 1,947.ii 25,742.33 27,6o9.49 o l5b lb 9 w4 " ? i s - * lob.u2 3. 93 >if Xri o r c t-i' *ocj Q i s c o v u o \no .co iii 1 o s \nd tion regarding the above difference, each of the major groups was considered independently. Computations involving t-tests were made and are presented in Table 12. ’ when Unimpeded I and II conditions were compared for the normally hearing group, a _t-ratio of 1.48 was obtained. This result was non-sig- nificant and feIi at approx1mate1y the sixteen per cent level of confidence. In similar manner the same comparison 72 of Unimpeded I and II conditions for the unilaterally deafened group resulted in a _t-score of 1.33, which was non-significant. This result falls at approximately the eighteen per cent level of confidence. TABLE 12 3IGFilr ICAUCE OF THE DIFFERENCE BET'vVEEi i LihAHS OF FREATMELiS UNIMPEDED I AinJ ULUMPhDED II FOR i nE ,.Oj .0 L L ; nrrSi'ilnO . • 1 . i f UHILa i Li I / ’ aLuY DE/-.F En ED GRGUPu Groups 1 X 0 3 . c i f l O ' f i c b Compared ’ L — V 3 t X 0 Obta ined Level of 3 ignif icance Unilatera11y deafencd Ur, I - Un 11 1.33 1 G/j (n o n — sig. ) ; o r m a r 1 y n earing — Unilaterally deafened Uni - U n i 2. 21 3b Normally hearing - Unilaterally deafened Un II - Un II 2. 03 4;o However, it should be noted that the t-score level for each inter-group comparison, while non-significant, should not be dismissed. Clinical performance seems to indicate that some effect, even though it may be minimal, tends to influence unimpeded reading following the applica tion of dst. deters and Van Voorhis stated that, although the result falls below the five per cent point, It means that there are more than b chances in 100 that accidents of fluctuation might account for one’s finding, and one must not be at all sure of any real differences among his 73 classes (10:359). Conversely, it also means that there are maybe 35 or 90 chances in 100 (8 or 10 to 1) that there are real differences and that one might be unjustified in hastily giving, up his hypothesis without further investiga tion. They stated that it is an error to over-readily accept the conclusiveness of our findings; but it is also an error to suppose thax an hypothesis has been fully re futed when it has merely been brought below the level of certainty. On the basis of a comparison between the F-score for the total group and t-scores for the two major groups, it was shown char the difference existed between the major groups rather than between conditions. However, the Unim peded I condition, since it was, so to speak, clinically pure, had to be considered as representative of true unim peded reading time, and possibly similar for the two groups. Since, as demonstrated in the r-score, a difference between groups existed, it was posited that the result could be attributed to she fact thax there was a greater carry-over effect into the Unimpeded II condition for the normally hearing group chan would prevail among the unilaterally deafened group because of being subjected to dst to two normal ears for a greater length of time than the "one eared" group. Since no statistically significant findings resulted from the t-tests described, it was necessary to compare the Unimpeded I condition with the- two total groups. The t-score obtained in this procedure of 2.21 was significant at the three per cent level, indicating a difference be tween groups in unimpeded reading prior to dst. A similar finding appeared when a t-scorc- was performed for the groups considered under Unimpeded II condition. The result of 2.03 was significant at the four per cent level, indica ting a difference between groups in post--dst unimpeded reading. (See Table 12.) Thus, it was demonstrated that both unimpeded conditions differed for the two groups. tained. (See Table 13.) Dst to the poorer ear among unilateral cases of the type included in the experiment, demonstrated a dst effect which was not similar to unimpeded reading. ings demonstrated that there was no difference within the group between pre- and post-dst unimpeded reading times. ing times were compared prior to dst application, there was a significant difference between the normal and unilateral as no iificant difference between the two unimpeded conditions for the un.ila terally deafened group, the possibility rtloafed that the soecia lly manipulated total group having dst to the poorer ear might sho sui'cs similar to uni rape-do core or b.ll, significant beyond the one per cent level, was ob In the case of each subject group, clear-cut find- These findings applied to both groups. However, 'when read 75 TABLE 13 ANALYSIS OF VARIANCE OF THREE TREATMENTS WITH THE UNILATERALLY DEAFENED GROUP: UNIMPEDED I, UNIMPEDED II, AND TOTAL READING TIMES OF DST TO THE POORER EAR Source of Variation Sum of Squares c l f Mean Square F Ratio P Between Groups 2,510.25 V 1,255.12 5.11 Within Groups 2S,742„7b ill 245.66 >1% Total 31,253.00 119 group. This via s also true ivhen the groups were compared considering post-dst reading time The nature of this difference can only be conjectured. It is possible, if the phenomen known as hard~of-hearing speech is a continuum, that the difference in reading times demonstrated in this experiment might be accounted for on the basis of the genesis of such a disturbance among the unilaterally deaf ened group and that such a disturbance might be first noted in a change in elapsed reading times. Although no statistically significant difference existed between Unimpeded I and II conditions with each group, it is concluded that the unimpeded reading time prior to dst application is clearly more desirable to obtain in the clinical setting, since no question of a possible dst effect comes Into this condition. It was also demonstrated that obtaining unimpeded oral reading times is clinically 76 feasible, since these results can adequately serve as a foundation for predicting dst involvement. Adaptation to dst Previous research has demonstrated that the maximum passage length per presentation level which remains stable before a lessening of the prolongation due to d_sis 400 syllables (60). In the present experiment, this problem of a lessening of the dst effect from Experimental I through Experimental II conditions was considered. 11 o adaptation existed for the unilaterally deafened group, for the dst reading time obtained from the better car condition was more prolonged in each case than that obtained from the condition to the poorer ear. The analysis of variance results, presented in Table 4, page 63, where Experimental I and I I conditions were combined for both groups, demon strated no significant difference between conditions for the groups. ’ when results obtained from the normally hear ing group under the same conditions, plus the specially manipulated column containing all dst times to the better ear among the pathological group, were analyzed, a non significant f-score of 2.92 resulted. (See Table 7, page 66.) Thus, it was possible to state that no adaptation occurred during these dst conditions with the normally hear ing group. Measures of central tendency and variability for this group under these conditions is presented in 77 Table 14. The mean v;as 7.9 seconds, v . ’ hich is well belov; the' arbitrary 10 seconds v;hich had been proposed in the dsl test referred to an svl . This iu s c c one cii sc rc nee was see up as the lease dirtcaencc aiiov;aole roe: accepting an organic unilateral case of more than 70 die difference in hearing acuity ten. e u Lais. .re noted in ten table, 77.0 ;jei cent oi the cat., s ndt. b? it'.; :a.. sccosft: , do.:, those normally .near mg ca;--„ s vi r._cn exce ccn.u an. as oaricrcncc, at snourG be noted that cyst speech ci recta rene ai’ . . : ays observed. This is not u . . . uc. 1 s ; : . ahs unilate ; . a 1 case, s , sonich sisov: a change an . ' 1 . n cn : . i r ' . i . c s . cu. . . to or s r a os. r : - r so car , a ^ v. t 11 a s time changes, i,“..jLr it . itf-.^a. .n 1 i.r ^-Tr r : . . . s s . . . ' t b • . i,. tbCO:, L>o bbTaalh :d.r:_..i:.h..T.ii. I .ihb d.hrHhldbdT.iL II T. r_. tr.wt T I . s . s Thi .. l..b.. vLL.y h . . : , - . . .1. .b o.sjU: , . .C c : ; i A Xi.'iC ■ f " ■ ' , ill . i a me ux r i . J i I i ( a . . . . 1 i .C C i.,r i s.. _,i : r ■ : re nee a d; . lev.' Id sec. del or; 10. u 7.9+a.79 a I . at-; . Or .1 - -i. y do (70.) 71 (77 . b,. t i n c e ;so d i r r c r s n c s "’r f e s t a b l i s h e d is l - n c n T);oc r i me n t a 1 ... a ; ;d I I c o n b i t i o n s tor: t h e n o r m a l l y h e a r i n g g r o u p , no s t a t i s t i c a l l y oi.... . 1 d i c a u t l e s s e n i n g or t h e d e l a y e d s i d e - t o : s e r r e c ^ a - .■ .. —.:. t i . o. u . r ..:... ... c .:: o c .■ . .. go. e s c n c ■ ^ a o n c u e t o a d a p t a t i o n . I n a d d i t i o n , s i n c e r.he re w a s a d i i f e r c n c c d e m o n s t r a t e d b e t w e e n the. e f f e c t s o l d s t a p p l i e d t o t h e poorer ear as compared with the application to the better ear, and in ail cases dst times to the better ear were more prolonged, no adaptation existed among the unilateral group. Pi scus sion Delayed sidetone is an excellent objective audio metric method, especially in the management of cases of exaggeration of hearing loss. Certain advantages in its use in the audiology clinic stand out. The subject, through the use of this technique, can be compared to himself. The response, the complicated process of attempting to monitor one5 s own disturbed speech, is much more reliable in the clinical setting, than the raising of a finger or the push ing of a button. In addition, the taped speech performance is an objective record of the test. In detecting differences between cars, the technique of dichotic presentation is excellent. In addition to sup porting or negating such a difference through rhe inter pretation of the temporal differences, we also have clear- cut major differences in the speaking process. When a true organic hearing loss of more than 30 db cxisxs in one ear, even though the timing of the passage may differ minimally from the unimpeded oral reading time, the initial phase of the test, dst to the poorer ear, produces speaking not too dissimilar from the unimpeded reading: the final phase of dichotic presentation of dst and noise, wherein dst Is 79 presented to the better ear, is strikingly involved and prolonged. This is considered to be a negative result of the unilateral d_st test. A positive result is obtained when each phase of the dst test presentation is similar in speech breakdown and in reading time results. There are clear-cut differences between positive and negative re sults. By contrast, certain other unilateral techniques produce only unclear differences due to limitations in the response. The Steager principle, often erroneously called test, is a clinical technique or a generalized procedure which has nt-vc-r been adequantly validated. 'Ahen applied in a clinical setting involving sophisticated malingering of all degrees among its population, the negative Stenger result, indicating a difference in hearing acuity between ears, must always remain suspect, since it requires simply the controlling of a finger response. In other words, a clear-cut positive Stenger response can be accepted without reservation. Any negative response must be suspected. This is true, also, with the Lombard, another general tech nique for dealing with unilateral cases. Again, a positive result is clearly acceptable, when there is a definite increase in vocal intensity. The negative result, however, as with the negative Stenger, must remain suspect since the response of raising vocal intensity can be rather easily controlled by a sophisticate. The dst test, in unilateral 80 application, by contrast, produces clear-cut dissimilar responses for both positive and negative results. CHAPTER V SUMMARY, CONCLUSIONS, AND IMPLICATIONS S unvnary The purpose of this lnve stigation was to determine what, if any, is the- difference in elapsed reading times of normally hearing and unilaterally deafened subjects which can be attributed to the dichotic application of delayed sidetone and masking noise. Subsidiary problems studied were the investigation of possible differences in unimpeded oral leading for these groups before arid after the dichotic application, as well as any possible adapta tion attributable 1 0 the delayed sidetone. The literature pertinent to the problem was reviewed in three main categories: (1) sidetone, (2) delayed side tone , and (3) the masking of speech. The experimental design chosen to explore the prob lem involved testing a total population of eighty veterans. Two equally divided groups were set up, of normally hearing and organically deafened subjects demonstrating unilateral hearing losses. The experimental group was selected on the basis of audiometric testing demonstrating normal hearing in one ear and a difference of 30 db or more for the deaf ened ear. A continuous prose passage 1600 syllables long, 81 taken from a fifth grade reader, was used for eliciting oral reading rates in the same manner for all subjects. There were four experimental conditions: (1) unimpeded oral read ing; (2) dichotic application of delayed sidetone and mask ing noise; (3) a second dichotic application, reversed from the initial presentation; and (4) unimpeded oral reading. The data, comprised of oral reading times, were treated statistically using F-scores and t-scores. Analyses of variance were computed for the entire population, as well as for the separate groups. In, addition, total dst condi tions and total non~cist conditions were treated for both groups. Also, an inter-group analysis of the dichotic dst and noise presentation was made for the unilaterally deafened group. Conclusions 1. Elapsed oral reading times of normally hearing and unilaterally deafened subjects differ under the dichotic application of dst and masking noise, being less prolonged when presented to the pathological ear. 2. Elapsed oral reading times obtained for each ear of a normally hearing subject do not ordinarily differ more than ten seconds under the dichotic application of dst and masking noise. 3. Elapsed oral reading times before and after the dichotic application of dst and masking noise are similar 83 for both normally hearing and unilaterally deafened sub jects, although there is a difference between groups for each condition treated independently. 4. No adaptation occurs during the reading of 8U0 syllables of prose during the two-phase dichotic applica tion of dst and masking noise, wherein both ears are tested for normally hearing or for unilaterally deafened subjects. b. One method of pro sentation of dichotic dst and masking noise to unilaterally deafened subjects produces greater time differences between reading results for the better and poorer ears, that method being presentation of dst to tiie poor er ear first. implications The present experiment has produced valuable infor mation, concerned with the clinical application of this unilateral dst test method} to add to previous clinical research material obtained in this professional area. By including a normally hearing subject group which could be analyzed independently, and which could be combined with a pathological group of unilaterally deafened subjects, it was possible to compare effectively the similarities and differences between these groups, Several interesting problems were raised by the con sideration of the data resulting from the experiment. It was concluded that these problems could lead to further investigation in the area of delayed sidetone. 84 The first of these problems concerned the need for additional information regarding the dichotic application of delayed sidetone. Since, as has been demonstrated in our previous research, dichotic application of dst and masking noise is as effective as bilateral presentation of dst, a valuable experiment would be the .invesligation of performance curves for single ears beginning at a lov; level of 10 or lb db and proceeding in 10 db steps upward in presentation intensity using reading passages of equal length for each presentation level. Sin.ce bilateral d st, used with cases alleging greater auditory deficit than actually exists, measures the better ear only and in doing so may lessen later dst application to the worse ear, such performance curves would determine whether or not the method is i S3 siolt. In sucn an expertrr* . on c , he oxciso tic pprica— tion for each ear should be compared with bilateral presen tation using the same presentation levels and reading pas sages. Such experimentation should include both normal and pathological groups. A second experiment might compare the effectiveness of other types of masking noise, such as white noise, with the complex noise used in this experiment. A still unmeas ured entity, and one which is worthy of further study, is the effective masking of internally generated sidetone over a range of noise presentation levels. A comparison of at least two different types of noise might suggest either that one noise is preferable to another or that they are equally effective as masking agents in such a study. The finding that dst elapsed reading times for pathological ears in the experiment differed from reading times to the normal ears and from unimpeded reading times implies that other differences may exist among specific pathological groups„ txperirncniation involving specific types of unilateral deafness, such as exclusively conduc tive or perceptive losses, should be of value in deter mining whether or not differences exist among these groups. Another problem suggested by the present experiment is the investigation of the dichotic application of dst and noise with cases shewing a difference in acuity in ears where the better ear is also pathological. Previous dich otic application has been concerned solely with those cases demonstrating hearing in the normal range in the bet ter ear. Another possible problem ace a is experimentation aimed at detecting a difference of less than 10 db between ears with the aim of refining the technique so that exact threshold determi.natj.or' ■ c:ou 1 d be achievcd. All of the experiments suggested above could be per formed in combination with GSh. They could also be con ducted with the aim of studying any possible sex differ ences by including groups of males and females. These and other problems point to the fact that 86 delayed sidetone testing is in need of further study and should provide an excellent opportunity for the development of exact clinical audiometric tests in the future, both for proper management of the difficult cases of exaggeration as well as assisting in authenticating true organic hearing losses. BIBLIOGRAPHY BIBLIOGRAPHY Books 1. Bond, Guy L., and Cuddy, Marie C. Days of Adventure. San Francisco: Lyons and CarnaharTCornparvyl 195117 44 0 pp. 2. Edwards, Allen L. Statistical_Ana1ysis. Mew York: Rinehart and Company, "~I946. 360 pp. 3. Flesch, Rudolf. Mow to Test Readability. Mew York: Harper arid Brothers, 1961. So pp. 4. Fletcher, Harvey. 7SeG!71 and Hearing in Communication. Hew York: D. Han Hostrand Company, 1963. 461 pp. 5. Heller j Morras r . , nnderman, tic mar a M. , a no S mge r, Ellis E. Finmctional Oto loc;y. lew York: Springer Publishing Company, Inc., 1966. 226 pp. 6. Hirsh, Ira J. The Measurementof Hearing. 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Fc stsre. Hung Deutsche Hedizinische V o c h e n s c h r i f t , 33 (1907) 97 0573 ■ ~~ ~ 54 . Stevens, S. S ., i . J l k r , G. , and T cuscoti, I. "The iV .a ski no o 1 5 pec-cn oy bine ,. a v e s , o gu a r t- r a v e s, and Regular and Modulated Pulse s ," J ournal ox the A cousti c a l Society of Ame r i c a , IS (194b) 418- 24. 55 . T iffany, G illia m R. , arid Hanley, C l a i r 2 , "Delayed Speech Feedback as a Test for Auditory M alinger ing ," S c i e n c e , 115 ( 1952) 59- 60 . ub . . 1 1 .u d a j > l a c i o C i i. o D c r a y o ci ~ i ci e — tone , " J our nol of 5 :-y c e c h and Hearing D isord e r s , 21 (19567 164-72 2 ..... 57 . ___________ , ar;d S u t h e r l a n d , Louis C. "A Simple Mechanical Adapter for V ariable Side-Tone D elay," J o u r n al of Speech and Hear in g D i s o r d e r s , 19 (195477 504- 506. 58 . W in c h este r, A. A. , and Gibbons, E. V .5 "Relative Ef f e c t i v e n e s s of Three Modes of Delayed Sidetone P r e s e n t a t i o n . 1 1 Arc.hive s of Oto 1 arynqology , 65 (1957), 275- 79 . 59 . _______________________ "The E f fe c t of Auditory Mask ing upon Oral Reading Rate," Jo u rnal of Speech and Hearing D iso rd e r s , 23 ( 1958 ), 250- 52 . 60 . _____________ _________ , and Krebs, D. F. "Adaptation t o Sustained Delayed S id e to n e ," Jour n a l of Speech 93 and Hearing Disorders, 24 (1929), 22-28. U n p u b11s h c d M at eriaIs 61. Boyer, Ernest Lehoy. "An Experimental Study of Speech Fluency under Stress as a Function of the Emotion ality of Speech Concent." Unpublished Ph.D. dis sertation, University of Southern California, 1928. 62. brungard , Jaccjue 1 ino . Cm expo rimen cat Invcstxgation into the Use of PCSE as an Adjunct to Delayed Side Tone." U n published i V , a s t e r 1 s t h e s is, U n i v e r sit y o f V . ' a s h i n g ton, 19 2 6. 63. Goodman-Malarnuth, II, Leo. "An Experimental Study of the Effects of Rate of Speaking upon Listenabii- ity." Unpublished Ph.D. dissertation, University of Southern California, 1926. 64. Huntington, Dorothy. "/in Experimeivtal I n v e s t i g a t i o n of the lie la tio.nship between Auditory Ability and Speech Disturbance: Produced by relayed Auditory Feedback." Unpublished Ph.D. dissertation, Uni versity of Illinois, 1922. 62. Jones, Merritt 3. "An Experimental Study of the Ef fects of Speech Rate on Audit: nee Judgments In Debate Situations," Unpublished Ph.D. disserta tion, University of Southern California, 1927. 66. Stromsta, C. A. "A First Approximation of the Dis tance from Vocal Cords to Cochlea arid the Transit Time of Bone-Conducted Sound from the Region of the Vocal Cords to the Region of the Cochlea." Unpublished Master1s thesis, Ohio State University, 1951. Pamphlet s 67. Fournier, J. E. The Detection of Auditory Malinger ing . Translations oT the Beltone Institute ior Hearing Research, 2900 West 36th Street, Chicago 32, Illinois. Government Repart s 68. Marpie, W., and Morrill, S. A. A Device for the 94 Production of Delayed Side-tone. U. S. Naval School of Aviation Medicine, Pensacola, Florida, 1951. Jt. Proj. Rept. No. 2, Bur. Med. Res. Proj, Mo. MM 001 064.01.08. 69. Rawnsley, A. I., and Harris, J. D. Comparative Anal ysis of normal Speech and Speech with Delayed Side-tone by Means of Sound Spectrograms. Bur. Med., Res. Proj. Mo. MM OO!? 041757)703, Med. Res. Lab., Rept. Mo. 248, 1954. Bell Laboratories 70. Foley, J. V'. "The Anti~Sidetone Station Circuit," Bell Laboratories Record. 463 West Street, New York, i\[ew”YorF7~Tt {1939) 347-50. 71. Principles of Hlectricity Applied to Telephone and and Telegraph Work. A Training Course Text Pre pared for Employees of the Long Lines Department American Telephone and Telegraph Company, 1953. n A n <. , i O p j - A * 72. Transmission Aspects of Improved Station Apparatus. Bell < and D; stem Practices, Transmission Engineering a, Educational Training Material, Section A B91 . 0 2 6 , 1 9 4 1 . 12 p p . 73. Transmission of Speech. Boil System Practices, Trans mission Engineering and Data, Educational Training Material, Section AB92.076, 1929. 24 pp. Monographs 74. Kryter, Karl C. "The Effects of Noise on Man," Jour nal of Speech and Hearing Disorders, Monograph Supplement I, 1950. 9b pp. lests 75. Gray, W. S. Standardized Oral Reading Paragraphs. Bloomington, Illinois: Public SchooT~PTIbTisHing Company, 1957. 4 pp. SHXIdMHrHV APPENDIX A CLINICAL INFORMATION FOR THE UNILATERALLY DEAFENED GROUP 97 TABLE 15 OTOLOGICAL DIAGNOSES AND SPEECH AUDIOMETRY RESULTS FOR THE UNILATERALLY DEAFENED GROUP Is . L L Ear ! T e r * Oted r arh.tar S s Age j PB D Otological Diagnosis P a t h » IJorm. jS RT Cor rect i. EB a ) C T . AD f < A 14,1Zjlb Coc ( - ■ 2. EP 30 Ab 32 98 o , a e , 1 j 1 o . x—■ J 24 Otological 3. MA O 1 2 1 1 A o L ) O 94 8,25,20,6,15, 17 1. Dead Laby- 4. cv 3 9 AS PR ‘ • _ ) 1j ,lo,14,aa r inth o. AD 27 ,Ho 60 80 i.3 .14 j 17 ,10 < — • 1 iypof unc- 6, A 1 \ 35 /v; ; ‘ t - ’ i'iR 13;IS s 28 t i o n , 7. Pi 3 43 i \ G > i bA : . P i 13,14,17 vo stibular r - O • 0;-i 36 4\jJ T \ b A 7 o i o ■ J a • ? _ V , f unction 9. r j i 66 o * - r e j 9-4 io,22,17 o v O , Labyrinthi 10. UiJ 24 Ao 0 0 LD0 , e i 16,18 t i s 11. DH 47 AD 66 ■ o 14 ? a a, id 4 . iv ;3 S ~ t 0 io 12. HM 31 r\D i i \ A 13 , .17 , 2 SCaio 13. CP 48 AD A A NR 1 o i d o ] !-• , J . o 5 a O v . ; , 1 d « j ’ .ia stoidc c- 14 -i. • - 9 36 Ab i ' i l 1 Art 13 ' 18 3 15 tomy IS. AC 3 6 r\ij 3 6 1 uo b , 19,6,Id.3 0 6. Ma stoiditi lb. JH Q A - Ac i ' . i i ; . i A 13,18,9 7, Otitis Ex 17. JG 24 / \ O i F t • . A 14 terna 13. AM 23 AS -2 96 O , - L 7 7 ; lb, a ’ 0 , 1 ' 0 Otitis i ' l o . i a 19. J M a AA- 5 0 98 S,2c.15 o j . Pseudo- 20. J D 45 AG : • i : 2 8,25,20,6,4, 14 10. Meniere ! s Tinnitus 21. LC 22 AS . ' 4 6 i 94 6,17,26,15 i I c n o 1 e s t c a— 22. DA 36 AD id N R 13,17 , 1 t oma 23. JM 52 AD 40 96 b,19,1o,5.3 0 12. Adenoids 24. CP 38 aD 85 id 14,17,22 25. AT 38 1 L i J 34 96 o,19,6.1b-5, 15 Deafn t s s 26. * ' 1 r A F ' A 4 4 AD 6 b 80 13 , 9 13, De a f no s s 27. EC 28 AD 65 98 5,18.16 14. Nerve Deaf 28. EE 32 AS 60 96 Sdoj 13 ,18 ness 29. CT 34 AS NR NR 13,17,29 15. Conductive 30. D R 33 AD NR i ' i R 14. 22 ,23,17 D. 31. riM 44 aD I jR NR 14'22,18 16. Mixed D. 32. DO 40 AD 4 8 96 8 , 17 ,4 , 16 17. Right Ear 33. r e s 36 AD 42 98 8,19j 24 18. Left Ear 98 TABLE 15 - Continued Ss 1st Ear Tested Path.Ear Age Path. Norm. SRI- PB % Cor rect Otological Diagnoses 34. JF 35. MP 31 67 AS AS 92 DR IIR hr 14,18 s22 14 j17, 22 General 36. RC 40 AS HR PR 14, 18 19. Purulent 37. WG 40 AD 45 94 5,11,20,15 20. Suppurative 38. BF 26 AD 70 62 14, 17. 22 21. Partial O r \ r- T r o y . r K 39 AS 54 90 16 , 21 22. Severe 40. LD 41 AD 48 96 8 , i 9 , 25 ,5 , 17,12 23. Total 24. Intermit tent 25. Chronic 26. Quiescent 27. Secondary 28. Cause Un determined 29. Following head in jury 30. Post-Opera tive APPENDIX B TABLES OF ELAPSED ORAL READING TIMES OBTAINED IN THE EXPERIMENT 100 TABLE 16 ELAPSED ORAL READING TIMES OBTAINED FOR THE NORMALLY HEARING GROUP (IN SECONDS) Unimpeded I Experimental I Experimental II Unimpeded II 105.8 157.1 139.0 92.6 101.3 125.8 115.8 99.4 121.4 162.. 6 145.2 103.2 100.6 126.7 129.0 106.1 103.9 138.2 132.0 100.5 101.4 117.6 124.8 106.7 103.8 145.0 146.5 93.5 111.8 127.0 124.5 112. 5 109.9 172.9 175.9 107.5 114.9 125.0 117.0 105.7 94.3 142.0 118.5 86.3 130.8 133.6 137.3 125. 0 109.9 113.5 114.0 102.2 92.0 128.3 132.7 86.4 105.0 143. 1 132.7 99.7 90.4 118.4 112.0 89.0 97.5 158.0 154.0 95 .8 94.3 107.7 106.6 96.4 92.0 119.7 114.7 86.1 99.0 108.6 113.6 98. 0 88.0 100.4 104. 1 86.7 91.3 102.2 136.9 89.6 100.2 130. 9 144. 8 96.4 116.9 136.0 136.7 114.3 96.6 129.1 130.3 104.6 98.8 139.1 157. 0 97.0 117.0 155.0 148.2 106.6 87.4 108.7 119.2 93 .4 99.0 174.5 172. 1 102.3 100.2 119.4 121. 0 95.6 113.8 139.0 137. 1 106.3 103.8 126. 1 130.4 95.8 86.2 104.1 102.4 86.1 119.6 199.5 203. 2 129.5 91.7 107.4 106.2 91.7 124.7 180.2 206.6 111.3 107.6 139.5 136.7 98.8 99.2 153.8 149.8 94.8 96.7 152.6 142.1 98.2 95.8 149.6 125.6 98.5 101 TABLE 17 ELAPSED ORAL READILG TIMES OBTAINED FOR THE UNILATERALLY DEAFENED GROUP (ill SECONDS ) Unimpededll 100.4 102.5 91.3 104.5 127.0 96.8 90.4 109.6 146.3 90.8 105. 8 120.7 96 .4 109.5 114.0 97.8 98.2 129.1 100.2 120. 2 90.1 129.0 114.3 109.0 141.7 105. 1 114.4 107.0 110.3 136.4 109.6 82.3 103.7 113.0 135.2 99. 0 98.5 101.9 119.0 102.3 perimental I 119.0 120.0 129.2 101. 0 162.7 106.8 113.4 117.3 163.0 110.5 141.2 119.6 128.0 118.7 122.1 110.2 145.5 121. 2 124 .6 134.0 J . 04.3 154.0 126.7 110.2 170.8 127.4 118.0 106.8 13 0.8 136.4 147.2 35. 9 134.5 130.4 210.6 109.8 114.1 97.5 132.0 104.9 E x p e r I rn e n t a 1 II 104.0 133.6 104.6 124. 0 149.1 126.4 93.8 139.1 149.8 14 0.5 117.0 219.2 91.3 150. 7 126.0 172.5 106. 2 161.0 109.0 zo Z, 4 93.9 286. 2 120.6 182.4 133. 0 143.5 109.2 123.4 114.3 152.4 107.6 112. 0 117.0 162.5 159.4 181.7 101. 0 123. 0 121.3 139.6 Unimpeded II 103.9 103.5 90.7 94.8 119.8 92.6 84.2 112. 0 137.3 86.1 106. 2 117.6 97.2 109.2 116. 0 97.5 98.6 129.1 94.3 138.0 85. 6 119.8 101.8 106.5 116.6 104.0 108.6 101.2 106. 2 125.7 100.8 76.8 90.4 111.8 128.8 97.4 93.0 91.0 114.1 97.8 APPENDIX C PRELIMINARY READING MATERIALS 103 GRAY’S ORAL READING TEST USED IN THE EXPERIMENT One of the most interesting birds which ever lived in my birdroom was a blue-jay named Jackie. He was full of business from morning till night, scarcely ever still. He had been stolen from a nest long before he could fly, and he had been reared in a house long before he had been given to me as a pet. INSTRUCTIONS READ ALOUD BY EACH SUBJECT No matter what you hear, please read this passage from beginning to end without hesitating, stopping or attempting to change your normal tone of voice. Don’t touch the microphone, and remember to speak as clearly and as normally as possible, and don’t begin to read until you receive the signal. APPENDIX D THE READING PASSAGE News about airplanes began at Kitty Hawk, North Carolina. Wilbur and Orville Wright proved that men could fly. Their airplane was in the air just a few minutes. It flew only a few hundred feet. Yet that flight brought changes to the world. It changed ways of travel. It changed the- way people thought about many things. Since December seventeenth, nineteen hundred and three there have been many flights. There have been many headlines about them in -newspapers. The Wright brothers worked hard to improve airplanes. There were other men interested in flying. These men learned what they could from others. They experimented. They wanted to make better airplanes. Glenn Curtiss was an American who thought that airplanes would be important He, too, made experiments. In nineteen hundred and eight Glenn Curtiss and his airplane both were in the headlines 106 This inventor and flyer went at a speed of thirty-nine miles per hour. Later, the Wright brothers flew forty miles per hour. People who read about such speed could scarcely believe it was true. Many people said that flying was foolish. People in other countries were interested in airplanes. Men in France, England, and other countries wanted to fly. These men studied, planned and experimented. In those days flying was dangerous. Sometimes headlines told of an airplane that had crashed. Flying over the land was dangerous enough. No one flew over water. In nineteen hundred and nine a French flier decided to fly to England. Me would fly over the English Channel— a distance of about twenty miles. His friends wanted him to change his mind. They feared he might crash and drown. But the French flier took off from France. 107 Soon the nows of his flight to England was in headlines all over the world. People wondered what changes the airplane might bring. Men would learn about flying. Airplanes might become safe for travel. Sometimes airplanes might flv faster and farther. People would be able to go from one country to another safely and quickly. They would get to know each other better. They would loam about each other's rays of living. They would become more friendly. It would be fine for the people of all the nations. Some people feared that airplanes might be used for war, too. Army and Navy men all over the world studied the use of airplanes. The United States Army and Navy bought airplanes. The airplar.es were made by the bright brothers. Charles Lindbergh was an air-mail pilot. He became acquainted with a number of men in Saint Louis. 108 These men learned that Lindbergh wanted to fly from New York to Paris, France. They got an airplane for him. The airplane was named Spirit of Saint Louis. Early on the morning of Pay twentieth, nineteen twenty-seven, Lindbergh took off in the Spirit of Saint Louis. He planned to make a non-stop flight across the Atlantic. Like a lone eagle he flew toward Paris. Thirty-three hours later the tired young pilot landed his airplane at a Paris airport. The Long Eagle, as people called Lindbergh, hud made a thirty-six hundred mile flight over the Atlantic. Four years had passed since Lindbergh's famous flight. A group of American Army fliers made a flight around the world. They left the United States on April ninth, nineteen thirty-one. The Army fliers visited many countries. They returned on September' twenty-eighth. 109 They flew twenty-six thousand, three hundred and forty- five miles. The names of two other American fliers wore in the news. They were Tost and Catty. They planned to fly around the world. rost and Gatty had planned to fly a short route. They had planned ro make stops to take on fuel. They did nor plan to visit in other lands. They wanted to go around the wsorld as fssr as they could. Everyone was inte rusted in this exciting I light. rost a no carry passso over snips. i he n c w s was se nr our oy 1 3 g i o . rreapi me s solo wnon they cropped ror xuel. an 1g - j o c iici, j i i _ l i i o a y s r 1 ^ ^ ; o vj l j *. c Dc c r we l ti c r r starting place. They had flown fifxeen thousand, four hundred ana seventy-four miles. They had shown that any parr of the world could be reached very quickly. Airplanes became much more important. At first they carried passengers only in daytime. 110 Then airplanes were improved. The airplanes could fly twenty-four hours a day. They flew in any kind of weather. Once people were afraid to fly at speeds of one hundred miles an hour. how they flew three hundred miles per hour. Flights over the ocean were made each day. Before nineteen forty-seven there was a terrible World 7 , ’ ar, Airplanes were important in that war. Thousands of them flew over enemy countries. It was said that huge umbrellas of airplanes covered the countryside. Great speed was needed for war airplanes. Men learned to fly faster. Experiments were made after the war was over. On October fourteenth, nineteen forty-seven, the headlines read: Airplane Flies Six Hundred Miles an Hour— Greater Speed may Be Possible. Headlines of nineteen forty-eight told about an airplane that flew seven hundred miles per hour. Ill Men kept on experimenting. They said that still greater speed was possible. They were right. Within a few months an airplane flew at fifteen hundred miles per hour. Headlines do not roll all the news about airplanes. People who travel want to know about improvements. They are interested in the safety and cornfort of air travel. Improvements have been made for safety in the air. Airplanes are we 11 built. Pilots are well trained. Airports air safer. Improvement has been m a d e - i n guiding airplanes. The pilots arc- guided in new ways. The pilots used to lis ten for signals. Signals told them if they were on the right course. The signals were long and short sounds. They were given by radio. Hot all of the airplane pilots use this kind of signal now. The pilot looks at the plane’s instrument board. A needle tells if he is on course. 112 He may be off it. The needle lets him know in which direction to fly to get on course. The instruments show how far he is from the nearest signal station. When the pilot gets near an airport, he gets information by radio. lie is told where and how to 1 and. Other airplanes may be landing or taking off. A pilot who is coming in may have to stay up for a while. He is told how high aoove the airport he is to fly. He goes as high as he is told to go. He circles above the airport until he is told to come in for a la riding. He carries plenty of fuel for this extra flying. Comfort is very important in air travel. Many airplanes are air-conditioned. They have comfortable seats. Some airplanes have seats which can be made into nice berths. There are dressing rooms on board. APPENDIX E DESCRIPTION OF THE MASKING NOISE 114 The type of noise used was the complex masking noise on the Allison audiometer, model 21 series. Ralph Allison, in a personal communication, has described the analysis made of his complex masking noise in his labora tories. Mis personnel made subjective tests and equalized the complex masking tone until they got as nearly as pos sible equal masking effect, at the various pure tone audi ometer frequencies so that the masking effect was within +5 db over the range from 500 to 4000 cps. In analyzing the complex noise spectrum over this range, in order to determine the requirements for equal masking at tire various test frequencies for pure tones, the following results were obtained: considering 500 cps, there are three components, at 440, 480 and 540 cycles; considering 1000 cps, there are three components, at 960, 1020 and 1030; considering 2000 cps, there are three com ponents, at 1930, 2040 and 2100 cps; considering 4000 cps, there are four components, at 3900, 3 960, 4020 and 4080 cps. The foregoing clusters produced equal masking at the frequencies considered, 500, 1000, 2000 and 4000 cps. At 4000 cps, where the components are closer to gether in frequency, they are somewhat below the level of the pure tone; and yet, due to the large number of compo nents, there is a slightly better than normal masking 115 effect. This is because the multiplicity of components results in an overall energy level that is greater than the energy in the pure tone. From this, it can be seen that the energy in the complex tone components must be equal to, or greater' than3 the energy in the pure tone for the masking to take place and only those components in the complex tone that are adjacent to the pure tone frequency will cause a masking effect. The oscilloscope characteristics show that the high frequency spectrum has very much higher voltages in it than the 1ow frequency spectrum; in fact, the 60 cycle signal is pretty well cancelled out, and the signal that remains has the fundamental of 12u cycles.

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Creator Gibbons, Edward William (author)

Core Title An Experimental Investigation Of The Dichotic Application Of Delayed Sidetone And Masking Noise

Degree Doctor of Philosophy

Degree Program Speech

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag OAI-PMH Harvest,Theater

Language English

Contributor Digitized by ProQuest (provenance)

Advisor [illegible] (committee chair), [illegible] (committee member), [Perkins, William H.] (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c18-54930

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Document Type Dissertation

Rights Gibbons, Edward William

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