PERFORMANCE or mousse INDUCED HEARINGJMPAIRED LISTENERS 0N ms COMPRESSED one MONOSYLLABLES Ms for the Degree of DA. A. MICHIGAN STATE L ' mm A; mm " 19?? °. ' '“mm ABSTRACT PERFORMANCE OF NOISE'INDUCED HEARING-IMPAIRED LISTENERS ON TIME COMPRESSED CNC MDNOSYLLABLES BY Sabina A. Kurdziel The purpose of this study was to investigate the effects of time compressed CNC monosyllables, presented at various sensation levels, on the discrimination ability of persons with noise-induced sensorineural hearing impairments. The experimental stimuli utilized were the feur lists of Form B of the Northwestern University Auditory Test No. 6 (NU-6). The words of each list were time compressed by 30% through 70%, in 10% steps, in addition to a 0% control condition. Compression was accomplished with the Zemlin modification of the Fairbanks Time Cbm- pressor. Nine males with noise-induced sensorineural hearing impairments participated in this study. Each subject was presented the six time compressed versions of the NU-6 test at feur sensation levels (16, 24, 32 and 40 dB), for a total of 24 experimental conditions. The 24 combinations of time compression and sensation levels were presented randomly, and the feur lists of Form.B of the NU-6 counter- balanced within these randomizations. In order to accomplish the testing, it was necessary for each subject to participate in two sessions. Sabina A. Kurdziel Results indicated that for sensorineural hearing-impaired subjects, the intelligibility of time compressed speech stimuli decreased gradually up to 60% time compression. A dramatic break- down in intelligibility occurred at 70% time compression. Results also indicated that lower sensation levels were necessary for op- timum discrimination at 0%, 30% and 40% time compression, whereas at 50% and 60% time compression, discrimination continued to im- prove as sensation level was increased. At 70% time compression, discrimination plateaued at 24 dB SL and remained essentially con- stant at 32 and 40 dB SL. Results also revealed that sensorineural subjects exhibited articulation fUnctions essentially similar in shape, though depressed, when compared to normal hearing listeners. There was considerable subject variability in performance among the sensorineural subjects on the time compressed CNC mono- syllabic words used in this study. This finding suggested that it would be difficult to predict which sensation level would provide the maximum discrimination score for a particular sUbject at speci- fic time compression ratios. Thus, if it is to be utilized clini- cally, it will be necessary fer time compressed Speech to be admin- istered to sensorineural subjects at several sensation levels. Based on both the present investigation and earlier studies, it appears that time compressed speech may have important clinical utility as part of a battery of central auditory tests. Hewever, considerable further research is needed. PERFORMANCE OF NOISE-INDIIIED HEARING-IMPAIRED LISTENERS ON TIME COMPRESSED CNC BlflKfiflllABLES By Sabina A. Kurdziel A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF ARTS Department of Audiology and Speech Sciences 1972 Accepted by the faculty of the Department of.Audiology and Speech Sciences, College of Cbmmunication.Arts, Midhigan State University, in partial fulfillment of the requirements fer the Master of Arts degree. Thesis Committee: 0d“? M... Chairman Q®w¢flg 9a.. 4%; f ACKNOWLEDGMENTS I gratefully acknowledge my thesis committee, Dr. William F. Rintelmann, Dr. Daniel Beasley and Professor.May Chin fer their assistance in this endeavor. I would also like to express my appreciation to Mr. Kenneth Brooks, Personnel Manager of the Melling Forging Co., for his inval- uable assistance in Obtaining sUbjects fer this study. A special thank you is also extended to my subjects fer their time and patience. I also wish to thank.Dr. Leo Deal, Maxine Haga and Don Riggs. Finally, I would like to thank all my friends fer their con- stant encouragement, understanding and.help. ii TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF APPENDICES . Chapter I. INTRODUCTION AND REVIEW OF THE LITERATURE Introduction . Tnme Compressed Speech Sensorineural Hearing Disorders . Summary and Statement of the Problem I I . EXPERIMENTAL PROCEDURES subjects Equipment Test Environment Experimental Stimuli Presentation Procedures . Analysis III. RESULTS . Time Compression and Intelligibility. Time Compression and Sensation Level. An unusual Case IV. DISCUSSION Time Compression and Intelligibility. Time compression and Sensation Level. Implications fer Further Research V. ERBMMWN'AND CONCLUSIONS LIST OF REFERENCES . APPENDICES iii Page iv ix 10 15 17 17 18 18 19 20 21 22 22 46 68 74 74 75 78 80 82 8S LIST OF TABLES Table Page I. Percent correct Speech discrimination (means and standard 23 deviations) as a fUnction of time compression and sen- sation level (N=8). iv LIST OF FIGURES Figure 1. Average articulation scores for six conditions of time compression plotted by sensation level; 8-32 dB SL (Beasley, Schwimmer and Rintelmann, 1972) and 40 dB SL (Beasley, Forman and Rintelmann, 1972). Typical audiometric configurations of noise-induced hearing losses resulting from 10 - 15 years exposure to drop ferge noise (Lindberg, 1971). Speedh discrimination in percent as a function of time compression at 16, 24, 32 and 40 dB SL. SpeeCh discrimination in percent (mean and i one standard deviation) as a function of time compression at 16 dB sensation level. Speedh discrimination in percent (mean and i one standard deviation) as a function of time compression at 24 dB sensation level. Speech discrimination in percent (mean and i one standard deviation) as a function of time compression at 32 dB sensation level. SpeeCh discrimination in percent (mean and i one standard deviation) as a function of time compression at 40 dB sensation level. Average articulation scores collapsed over sensation level, plotted by time compression conditions, illustrating similarities in slopes of functions between normal-hearing (Beasley, Schwimmer and Rintelmann, 1972; Beasley, Forman and Rintelmann, 1972) and sensorineural groups. Individual subject perfbrmance in percent, as a function of time compression at 16 dB sensation level. Page 14 27 29 31 33 35 37 39 Figure Page 10. Individual subject perfbrmance in percent, as a 41 function of time compression at 24 dB sensation level. 11. Individual subject perfbrmance in percent, as a 43 function of time compression at 32 dB sensation level. 12. Individual sdbject perfbrmance in percent, as a 45 function of time compression at 40 dB sensation level. 13a. Speech discrimination in percent, as a function of 49 time compression, at all sensation levels for subject 1. 13b. Speech discrimination in percent, as a function of 49 sensation level, for six conditions of time compression for SUbject 1. 14a. Speech discrimination in percent, as a function of 51 time compression, at all sensation levels for subject 2. 14b. Speech discrimination in percent, as a fUnction of 51 sensation level, for six conditions of time com- pression for subject 2. 15a. Speech discrimination in percent, as a function of 53 time compression, at all sensation levels for subject 3. 15b. Speech discrimination in percent, as a function of S3 sensation level, for six conditions of time com- pression for SUbject 3. 16a. Speech discrimination in percent, as a function of 55 time compression, at all sensation levels for SUbject 4. 16b. Speech discrimination in percent, as a function of SS sensation level, for six conditions of time com- pression fer Subject 4. 17a. Speech discrimination in percent, as a fUnction of 57 time compression, at all sensation levels for SUbject 5. vi Figure Page 17b. Speech discrimination in percent, as a function of 57 sensation level, for six conditions of time com- pression for Subject 5. 18a. Speech discrimination in percent, as a function of 59 time compression, at all sensation levels for SUbject 6. 18b. SpeeCh discrimination in percent, as a function 59 of sensation level, for six conditions of time compression for SUbject 6. 19a. SpeeCh discrimination in percent, as a function 61 of time compression, at all sensation levels for subject 7. 19b. Speech discrimination in percent, as a function 61 of sensation level, for six conditions of time compression fer subject 7. 20a. Speech discrimination in percent, as a function 63 of time compression, at all sensation levels for SUbject 8. 20b. Speech discrimination in percent, as a function 63 of sensation level, for six conditions of time compression fer SUbject 8. 21. Discrimination in percent as a function of sensa- 65 tion level at six conditions of time compression, (N=8) O 22. Average articulation scores collapsed over time 67 compression, plotted by sensation level, illustrat- ing the performance of normal-hearing (Beasley, Schwimmer and Rintelmann, 1972; Beasley, Fbrman and Rintelmann, 1972) and sensorineural groups. 23a. SpeeCh discrimination in percent, as a function 71 of time compression, at all sensation levels for subject 9. 23b. Speech discrimination in percent, as a fUnction 71 of sensation level, for six conditions of time compression for SUbject 9. vii Figure Page 24. Pure tone audiogram of Subject 9. 73 viii LIST OF APPENDICES Appendix Page A. Initial Letter Sent to Subjects 85 B. History of Neise Exposure 87 C. Mean Audiogram and Individual Audiograms 90 D. Calibration of Equipment 100 E. Instructions Given to Listeners 105 F. Answer Fbrm USed by Listeners 107 G. 4 Lists of Fbrm B NU Auditory Test No. 6 109 H. Order of Presentation of NU Auditory Test No. 6 111 I. Test Results of 9 Subjects 115 ix CHAPTER I INTRODUCTION AND REVIEW OF THE LITERATURE One of the problems encountered in utilizing audiological tests designed for isolating site of lesion in the central auditory pathways is, that often, these tests are employed with central nervous system cases befbre they have been adequately standardized on normal listeners or documented with behavioral responses of in- dividuals having peripheral lesions. .A review of the literature suggests the importance of dis- torted Speech tests in the diagnosis of lesions in the central ner- vous system (Matkin and Olsen, 1971). Filtered Speech was utilized by Bocca (1955), Bocca, gt_a1;_(1955), Calearo (1957) and Jerger (1964). Periodically switched speech and periodically switched noise were employed by Calearo and DiMitri (1958) and Calearo, et_al;_ (1962). Matzker (1959) used a frequency filtering method and Katz (1962) utilized a competing message for identification of lesions in the central nervous system. Another fbrm of distorted Speech test that has received con- siderable interest as a potential diagnostic tool for identification of lesions in the central auditory system is time compressed speech. A review of the literature suggests that time compressed speech may be used in the diagnosis of lesions of the central auditory path- ways; however, methods of time compression utilized to date have not been clearly defined. The experimental stimuli have also varied from monosyllabic words, (Luterman, Welsh and Melrose, 1966; Sticht and Gray, 1969) to sentential material (Calearo and Lazzaroni, 1957; deQuiros, 1964; Bergman, 1971). Partly, because of these differences, it has been difficult to clinically apply time compressed Speech. To obtain a clinically useful test, procedures for time compression must be well defined and clinically standardized test materials must be utilized. Normative data on varying percentages of time compression have been Obtained by Beasley, Schwimmer and Rintelmann (1972) and Beasley, Fbrman and Rintelmann (1972). These investigators defined the method of time compression employed and utilized a clinically standardized word list fer the experimental stimuli. They emphasized the impor- tance of obtaining data on conductive, cochlear, retrocochlear and central nervous system disorders. Because data is needed on different populations in order to develop a clinically useful test, this study will apply the same experimental Stimuli used by Beasley, Schwimmer and Rintelmann (1972) and Beasley, Forman and Rintelmann (1972) to a group of individuals 'with cochlear pathology. SUbjects with noise-induced hearing im- pairments were Chosen because the cochlear lesion is usually restricted to the hair cells of the Organ of Corti (Rosenberg, 1967; Davis and Silverman, 1970). Time compressed Speech The importance of the time factor in speech discrimination has been emphasized by Fburnier (1956). He noted that in the el- derly the cortex requires increased time for identification of a message. He related this specifically to the difficulties in Speech discrimination encountered by the aged. Bordley and Haskins (1955) concluded that an increased difficulty in intelligibility is evi- denced in the aged, when words are presented at a high average syl- labic rate. Finzi (1955) utilized various rates of accelerated speech with presbycusic subjects and attempted to determine their speech reception thresholds. He feund that the speech reception threshold may rarely be reached when accelerated.material is utilized as the acoustic stimuli. Calearo and Lazzaroni (1957) conducted a study whereby aged subjects responded to "short significant senstences" recorded at several accelerated speech rates. The sentences were recorded at the rates of 140, 250 and 350 words per minute (wpm). They fbund a dramatic deterioration in discrimination ability with material pre- sented at 350 wpm when elderly subjects were compared to normal hear- ing subjects. Under SUCh accelerated conditions, none of the aged SUbjects obtained a speeCh reception threshold, nor did they receive higher than a 50% discrimination score. The same distorted speech stimuli was presented to subjects with lesions of the temporal ldbe. It was feund that poorer discrimination scores were obtained when the stimuli were presented to the contralateral ear. Although Calearo and Lazzaroni have shown that lesions of the temporal ldbe can be detected with accelerated Speech, they failed to provide nonnative data and controlled time compression conditions. DeQuiros (1964) utilized the same rates of accelerated Speech as Calearo and Lazzaroni (1957). However, the experimental stimuli consisted of longer (10 word) sentences. The distorted speech was administered to normal and presbycusic subjects, subjects with per- ipheral hearing impairments and subjects with central disorders. The results of the investigation indicated that there was a marked de- terioration of discrimination.ability at the highest rate of speech in subjects with cochlear pathology. Results of this study also gave evidence that accelerated Speech testing may provide additional in- formation in the diagnosis of brain lesions within the temporal ldbe. DeQuiros emphasized, however, that accelerated Speech tests must be used in conjunction with other audiometric tests. Bocca and Calearo (1963) reported that aged sUbjects ex- perienced greater difficulty in responding to phrases spoken at an accelerated rate than younger persons. They stated that "central acoustic reaction time" was lengthened as a result of the aging pro- cess. Pestalozza and Shore (1955) also identified a "defect in cor- tical reaction time" in aged sUbjects. They found that aged subjects experienced great difficulty in interpreting speech presented at an accelerated rate. Luterman, Welsh and Melrose (1966) utilized both an aged population and two groups of younger adults in their study. They presented their listeners with phonetically-balanced CID W-22 word lists under conditions of normal rate and 10% and 20% time compression. Time compression in this study was accomplished via an electromeChan- ical sampling technique. Their results indicated that all sUbjects responded in a similar manner. The percentages of time compression utilized relative to the unaltered condition were detrimental to all three groups. Hewever, their findings were limited in terms of the ratios of time compression utilized. Sticht and Gray (1969), using the electromechanical sampling method, investigated speech intelligibility of time compressed pho- netically-balanced (CID W-22) words fer young and aged normal and sensorineural hearing-impaired Subjects. They used a control condi— tion of 0%, and experimental conditions of 36%, 46% and 59% time com- pression. They fOund that discrimination of time compressed.words was not affected differentially by the nature of the subject's hear- ing ability. Results did indicate, however, that discrimination ability of the aged listeners was affected.more than that of the younger listeners under time compression, and that this difference increased as the percentage of time compression was increased. Sticht and Gray, however, did not use a large enough population (28 sUb- jects) to establish normative data and Obtain clinically usable arti- culation functions. They also utilized a limited number of time com- pression conditions. Bergman (1971) tested the hearing fer speech of adults in each age decade from 20 - 89 years under several difficult listening con- ditions. Results of his study indicated that the understanding of speech under conditions of distortion, time alteration and competing signals showed dramatic deterioration, even though conventional audiometric configurations revealed relatively normal hearing fer pure tones. Bergman suggested that this deterioration is somehow related to a decrease in time-related processing abilities. In a carefully controlled Study by Beasley, Schwimmer and Rintelmann (1972), 96 normal-hearing young adults were administered six different percentages of time compression (0%, 30%, 40%, 50%, 60% and 70%) at fOur different sensation levels (8, 16, 24 and 32 dB). The experimental stimuli used in this study were the feur lists of Fbrm B of Nerthwestern University Auditory Test No. 6 (NU-6) (Tillman and Carhart, 1966): I The NUe6'word lists were chosen as the experimental stimuli for this study because they have been standardized with both normal and pathological listeners. Tillman and Carhart (1966) administered these tests to three groups of Subjects: normal hearing persons, those with conductive impairments and those with sensorineural hearing losses. Articulation curves were plotted as a function of sensation level. The inter- and intra-list reliability was found to be good. Further, the slope of the articulation function was found to vary ac- cording to the status of the auditory system; that is 5.6% per dB fer the normal hearing and conductive populations and 3% per dB fer persons with sensorineural hearing impairments. Beasley, Schwimmer and Rintelmann (1972) recorded the feur word lists of NU-6 and taped them according to the method advocated by Rintelmann and Jetty (1968). The experimental tapes were then tem- porally processed using the Fairbanks electromechanical time com: pression apparatus (Fairbanks, Everritt and Jaeger, 1954) as modi- fied by Zemlin (1971). Each list was time compressed.by 30%, 40%, 50%, 60% and 70%. .A control condition of 0% time compression was also utilized. The sUbjects were divided into six groups corresponding to the six ratios of time compression. Each sUbject was then presented with the four lists at a specific percentage of time compression at each of the feur sensation levels. Results indicated that as the percentage of time compression increases, intelligibility decreases. The decrease in intelligibility is gradual over the conditions of 30% - 60%; however, it was feund that at 70% a dramatic breakdown in intelligibility of time compressed speech occurred (Figure 1). Results also indicated that the intelligi- bility is affected by sensation level. It was feund that discrimina- tion ability at each condition of time compression increased as sensa- tion level increased. A.study by Beasley, Ferman and Rintelmann (1972) utilized the same experimental stimuli as the Beasley, SChwimmer and Rintelmann (1972) study, to determine the responses of 16 normal-hearing young adults to the Six conditions of time compression at a 40 dB sensation level. Results were similar to those obtained in the Beasley, Schwimr mer and Rintelmann (1972) Study, which utilized lower sensation levels; that is, intelligibility decreased as time compression increased, with Figure 1. Average articulation scores for six conditions of time compression plotted by sensation level; 8-32 dB SL (Beasley, Schwimmer and Rintelmann, 1972) and 40 dB SL (Beasley, Forman and Rintelmann (1972). 0? $55 2033 VN 2 _ «on woo mgm woe 3m 8 A O. a 8 8- 8 1332mm .INEDUHd 3 10 a dramatic breakdown in intelligibility occurring at 70% time com- pression (Figure 1). As stated earlier, if a diagnostic measure is to become clini- cally useful, data must be Obtained on normal-hearing young adults by applying controlled time compression procedures to a clinically stan- dardized speech discrimination test. The studies by Beasley, Schwimmer and Rintelmann (1972) and Beasley, Fbrman and Rintelmann (1972) have accomplished this. These authors have stressed that other clinical populations should be examined. There is a need to collect similar data on individuals with coChlear and retrocoChlear lesions, as well as persons with central nervous system disorders. The present inves- tigation will fecus on individuals having coChlear lesions. Sensorineural Hearing Disorders An understanding of sensorineural hearing loss is important in order to examine distorted speeCh tests in relation to clinical appli- cation. Thus, a review of sensorineural hearing loss and its parameters is presented below. Davis and Silverman (1970) stated that the term sensorineural hearing loss implies an abnormality of the sense organ, the auditory nerve or‘bothl They further stated that dysacusis or "faulty hearing" may be due to malfUnction of the sense organ, or it may be due to ab- normal function of the brain. A.pure sensorineural hearing impairment eXists when the outer and middle ear are functioning properly. Sound is conducted to the inner ear, but it cannot be perceived or analyzed correctly. The typical sensorineural loss is characterized by better 11 hearing for the lower frequencies than for the high frequencies. Sensorineural hearing loss has a multitude of causes (Rosen- berg, 1967). Shambaugh (1967) lists twenty common types of sensori- neural losses, including congenital deafness, endolymphatic hydrops, acoustic neurinoma, presbycusis and noise exposure. Shambaugh also stated that certain types of sensorineural losses can be of central origin. For example, multiple sclerosis can sometimes produce a sensorineural type hearing impairment. This is thought to be due to the interruption of the auditory pathways within the brain stem. Shambaugh emphasized, however, that diseases of the central nervous system.are usually not accompanied by a loss of hearing. The most common cause of sensorineural hearing impairment is presbycusis. Sensory processes tend to deteriorate with age. The de- terioration begins at approximately age 30 and becomes increasingly no- ticeable with each decade. Presbycusis usually reaches the State of a handicap in a person between the ages of 60 and 70 (Rosenberg, 1967). In preSbycusis the higher frequencies are affected first. The audiogram diSplays a bilaterally symmetrical sloping hearing impair- ment. The air and bone conduction thresholds are interweaving, with normal or nearly normal hearing at the lower frequencies. Discrimina- tion is difficult fer the presbycusic because of the loss of high fre- quency consonant sounds. Some cases of presbycusis are accompanied by phonemic regres- sion (disproportionate loss of the ability to understand speech). AS a result of the aging process, a degeneration of the central nervous 12 system, including the higher auditory pathways, occurs (Shambaugh, 1967). Another common cause of sensorineural hearing loss is exces- sive noise exposure. Many industrial noises are of sufficient mag- nitude to produce permanent damage to the nerve fibers in the cochlea (Rosenberg, 1967). People working in excessive noise (drop forges, metal working plants, jet aircraft) can have damage to the hair cells to such an extent as to produce a socially handicapping, permanent loss of hearing. The audiometric configuration of a noise-induced hearing impairment shows a sloping air and bone conduction curve, reaching its deepest point at 3000 or 4000 Hz. There may be some slight recovery at higher frequencies. In some cases the loss continues to deepen and widen after noise exposure has ceased (Shambaugh, 1967). People with noise-induced hearing impairments do not experience phone- mic regression, since according to Rosenberg (1967), only the hair cells of the cochlea are typically involved. Lindberg (1971) investigated permanent threshold shifts of 71 drop ferge workers. He reported that after about 10 - 15 years of ex- posure to impulse noise in a drop ferge hammer shop, the typical audio- metric configuration displays either a steeply sloping audiometric con- figuration or a gradual sloping configuration (Figure 2a and 2b). The discrimination ability of persons with sensorineural hear- ing impairments is lowered in comparison to normal hearing persons or those with conductive losses. Carhart (1946) stated that there is a relationship between the hearing loss fer pure tones and Speech discrim- 13 Figure 2. Typical audiometric configurations of noise-induced hearing losses resulting from 10-15 years exposure to drop ferge noise (Lindberg, 1971). 14 p P n n N Nuke: :fl xucosoopm ooow oooq ooom coca oom P 0mm u om ow oq om (V961 ‘OSI) 8p ut IeAeq Buriean ooom coca o » mm Nuke: cw zoomsoopw ooow oooe om — 0mm p cm 00 oq om (V961 ‘031) HP u: IBAGT Butleau 15 ination. The frequency range important for understanding speech is approximately 250 - 4000 Hz. If a person has normal hearing within this range, his discrimination score will be approximately 90% - 100%. However, if pure tone thresholds in this range become poorer, discrimr ination will also become poorer. various researchers have noted that the speech discrimination score is in good relation to the pure tone configuration and audiometric reduction (Pestalozza and Shore, 1955; Thompson and Hoel, 1962; Gollesberg and Plath, 1967). Summary and Statement of the Problem Theoretical and diagnostic implications of time compressed speech with reference to central auditory disorders have been discussed (Beasley, Schwimmer and Rintelmann, 1972; Bocca and Calearo, 1963; Calearo and Lazzaroni, 1957; deQuiros, 1964 and Sticht and Gray, 1969). Studies which have investigated the potential of time compressed speech as a diagnostic tool have failed to provide normative data (Calearo and Lazzaroni, 1957; Bocca and Calearo, 1963; deQuiros, 1964; Sticht and Gray, 1969). Other studies have also utilized limited ratios of time compression (Sticht and Gray, 1969; Luterman, Welsh and Melrose, 1966). Sticht and Gray and Luterman, et_al; also utilized the CID W-22 speech discrimination test as the experimental stimuli. As stated by Carhart (1965), the W-22 word lists may not be effective in a differential diagnosis as the word lists are too easy. Beasley, Schwimner and Rintelmann (1972) and Beasley, Forman and Rintelmann (1972) have Obtained normative data using a time compressed version of the Nerthwestern University Auditory Test No. 6. Results 16 of their studies indicate possible clinical application of this par- ticular test; however, further research is needed to examine the ef- fects of time compressed.monosyllabic CNC words on the discrimination ability of subjects with conductive, cochlear, retrocochlear and cen- tral nervous system disorders. It is the purpose of this study to investigate the effects of time compression on the discrimination ability of persons with coChlear pathology. SUbjects with noise- induced hearing loss were selected because, unlike presbycusis, the site of lesion is restricted to hair cell damage within the Organ of Corti (Rosenberg, 1967; Shambaugh, 1967). The specific purpose of this study is to examine the effects of varying percentages of time compression on monosyllabic word in- telligibility as a function of sensation level upon subjects with bi- laterally symmetrical noise-induced hearing impairments. Thus, the following questions will be investigated: 1) Will different percentages of time compression (30% - 70% in 10% steps) result in differential intelligibility scores among persons with a noise-induced sensorineural hearing impairment? Further, how will the results compare to the data on normal hearing persons? 2) Will the intelligibility scores at the varying percentages of time compression interact with sensation level in this population? .Also, will the results be comparable to data on normal hearing listeners? 3) Will Specific subjects Show differences in response ability on this task? CHAPTER II EXPERIMENTAL PROCEDURES In this Study nine subjects with bilaterally symmetrical noise-induced hearing impairments received the Northwestern University Auditory Test No. 6 at six percentages of time compression at feur sensation levels for a total of 24 word lists per Subject. SUbjects Nine subjects with an age range of 28 years 2 months to 53 years 3 months and a mean age of 44 years 9 months were utilized. The subjects were employed at one of the drop forges in the Lansing area. EaCh subject was initially contacted by letter (Appendix A), and given a detailed questionnaire concerning his history of noise exposure (Appendix B). All subjects were then required to take a.bi1ateral pure- tone air- and bone-conduction test at octave intervals from 250 through 8000 Hz to insure a bilaterally symmetrical noise-induced sensorineural hearing impairment. Subjects with a conductive component of 15 dB or more for the Speech frequencies (500, 1000 and 2000 Hz) and pure tone averages of 30 dB or better and 70 dB or poorer were excluded from the study. A.tape recorded version of the CID W-l spondee word list was administered.bilaterally to obtain speech reception thresholds. The ear 17 18 with the best speech reception threshold, within the experimental limits of the design, was then selected as the test ear. The median audiogram.and individual audiograme of each sub- ject are in Appendix C. Equipment To obtain pure tone audiometric data, a Maico audiometer, (Model MA 24), was used to drive TDH-39 transducers mounted in MX 41/AR cushions. .A Grason Stadler Speech audiometer (Model 162) was coupled with a tape recorder (Ampex 602-2) to drive the TDH-39 transducers mounted in MM 41/AR cushions to present the CID W—l spondee word lists and the experimental stimuli. Calibration of the equipment took place before, during and after the experiment. No important systematic changes were noted in the output of the equipment during the course of this investigation. Ca1- ibration procedures are presented in Appendix D. Test Environment The subjects performed their listening tasks in a sound- treated booth (pre-fabricated double-walled 1200 series IAC test cham- ber) which contained earphones and an intercoml The overall level of the ambient noise in the test chamber measured 48 dB SPL on the C Scale of the Brfiel and Kjaer Sound Level Meter (22048). Measuring the noise with octave band filters, the most intense component was found to be the 31.5 and 63 Hz bands, which had levels of 44 and 31 dB SPL respec- tively. The level of the noise in the 125 and 250 Hz octave band was 19 20 and 17 dB SPL respectively. The levels of the octave bands from 500 through 8000 Hz were below 10 dB SPL. These levels were suf- ficiently low so as not to interfere with the subject's listening task. The experimenter and the test equipment were in an adjacent single-walled IAC control room. .All equipment utilized was located in the Audiology and Speech Sciences Building at Michigan State Uni- versity. Experimental Stimuli The experimental stimuli utilized in this study were the four lists of Ferm.B of Northwestern University Auditory Test No. 6 (Til- lman and Carhart, 1966). Each list is composed of 50 monosyllabic CNC words. The words have been phonemically balanced as recommended by Lehiste and Peterson (1962). The four word lists were recorded locally at normal conversational speech and effert level by a trained white male talker who spoke General American English under controlled record- ing procedures. These lists were found to be essentially equivalent and to demonstrate good inter- and intra-test reliability (Rintelmann and Jetty, 1968). As explained by Beasley, Schwimmer and Rintelmann (1972), copies of each tape were temporally processed using the Faifibanks electro- mechanical time compression apparatus (Fairbanks, Everritt and Jaeger, 1954), as modified by Zemlin (1971). Each list was time compressed by 30%, 40%, 50%, 60% and 70% in addition to a 0% time compressed condition, 20 resulting in 24 experimental tapes. Presentation Procedures Each subject was seen twice with each experimental session lasting two hours. During the first session each subject was given a conventional pure-tone air- and bone-conduction test bilaterally. The CID W—l Spondee word list was then administered.monaurally under earphones to both ears, to obtain speech reception thresholds (SRT), and to determine the test car: The ear with the best SRT within the limits of the experimental design was designated as the test ear. Prior to the presentation of the experimental stimuli, the subject received a set of instructions (Appendix E) and a set of ans- wer forms for writing his responses to the monosyllabic word lists (Appendix F). Each subject was then presented with the feur lists of Ferm.B of the NU-6 (Appendix G), at four Sensation Levels: 16, 24, 32 and 40 dB at each percentage of time compression: 0%, 30%, 40%, 50%, 60% and 70%. For each subject each.time-compressed condition was pre- sented four times, that is, once at each sensation level, fer a total of 24 conditions within two test sessions. Half of the word lists (12) were presented during the first test session and the other half were presented about one week later, during the second session. In no case did more than eight days elapse between the first and second test ses- sion for any subject. The time compression conditions and the sensation levels were randomized and the lists were counterbalanced to the ran- domizations (Appendix H). 21 Analysis The experimenter hand-scored the data and converted them to percent correct scores. The subject's scores were individually plot- ted at eaCh sensation level over the varying percentages of time com- pression. lMean percentage scores were also determined fer each per- centage of time compression. CHAPTER III RESULTS The results of this study generally support the thesis that as the ratio of time compression increases, intelligibility decreases among sObjectS with noise-induced sensorineural hearing impairments. The data are presented as mean values and, in some instances, standard deviations are Shown. Also, individual data are displayed and dis- cussed in relation to the means. Further, one subject (No. 9), due to his unusual response characteristics, is discussed individually. Results are reported in Table I and Appendix I and are shown in Figures 3 through 24. Time Compression and Intelligibility Mean results for eight subjects Show that different percentages of time compression result in differential intelligibility scores fer noise-induced sensorineural hearing-impaired individuals. Table I and Figures 3 through 7 indicate that intelligibility decreased as the ratio of time compression increased. Table I and.Figure 3 show that there is a gradual decrease in intelligibility from 0% through 60% time compression and that at 70% time compression a dramatic breakdown in intelligibility occurs at all sensation levels. Hewever, no trends in amount of reduction in per- 23 Table I. Percent correct Speech discrimination (means and standard deviations) as a function of time compression and sensation level (N=8). 16 dB 24 dB 32 dB 40 dB 0% x 63.75 68.50 72.50 66.50 SD 14.64 9.37 13.97 10.70 30% E 57.00 66.25 63.00 60.00 SD 13.40 13.33 14.93 15.97 40% x 48.25 47.50 56.50 55.75 SD 14.60 16.38 21.00 16.95 50% R 43.75 47.50 56.75 58.50 SD 20.04 15.03 19.30 17.23 60% E 31.50 38.25 43.25 44.00 SD 12.44 15.87 17.33 20.23 70% i 3.50 8.75 8.75 9.25 SD 4.87 9.50 8.55 9.68 24 centage scores between time compression conditions is evident. Fig- ure 3 also shows that at 40%, 50% and 60% time compression, subjects perfbrmed clearly better at the higher sensation levels (32 and 40 dB). Figures 4 through 7 demonstrate the perfbrmance of the SUb- jects over each ratio of time compression with each figure showing only one sensation level. .At all sensation levels except 16 dB, a plateau- ing effect between 40% and 50% time compression occurs. There is even a slight improvement at 50% time compression at 40 dB SL. Hewever, at 16 dB SL, the reduction in intelligibility was consistent as a fUnction of increase in compression. Figures 4 through 7 also demonstrate the wide range in scores Obtained at each condition of time compression and sensation level. The Spread of scores around the mean, as exhibited by the standard deviations, is relatively large at all conditions of time compression. Figure 8 displays the average articulation scores fer all sen- sation levels, plotted by time compression. This illustrates the Sim: ilarities in SlOpes of functions between normal-hearing individuals as gathered by Beasley, Schwimmer and Rintelmann (1972) and.Beasley, For- man and Rintelmann (1972), and sensorineural hearing-impaired indivi- duals. .A reduction in intelligibility in the sensorineural group can be noted over all conditions of time compression in comparison to the normal-hearing group. Except for a slight plateau at 40% to 50% time compression in the sensorineural group, the parallelism to normals evident in the slope of the function is quite remarkable. 25 Figure 8 also illustrates that in the normal hearing population, % and 30% time compression scores were almost identical. The normals then consistently dropped at 40%, 50% and 60% time compression. In the sensorineural group, a small deterioration in discrimination im: mediately begins at 30% time compression. They then continue to drop with a plateau occurring at 40% - 50% time compression. Both groups Showed a dramatic breakdown in intelligibility at 70% compression. Recognizing that given individuals often deviate considerably from group means, it was felt important to diSplay the results of each subject. The performance of each subject is therefore shown in Fig- ures 9 through 12. Each figure displays the individual perfOrmance of each subject over each time compression condition, with every figure showing only one sensation level. Considerable variability in perfOr- mance both among and within subjects is evident at eaCh sensation level. Each sUbject exhibited basically two types of response curves over the six conditions of time compression. Figures 13a through 17a illustrate that Subjects 1 through 5 display gradually decreasing scores at 0%, 30%, 40% and 50% compression, with a definite drop in perfbrmance at 60% time compression. A dramatic breakdown in intel- ligibility then occurs at 70% time compression. Figures 18a through 20a show that Subjects 6 through 8 demonstrated gradually decreasing scores from 0% through 60% time compression, with again a dramatic breakdown in intelligibility occurring at 70% time compression. 26 Figure 3. Speech discrimination in percent as a function of time compression at 16, 24, 32 and 40 dB SL. 27 LLLL SSSS aaaa 6420 1234 == == x000 ‘0 I1 I 00X 1 .bFPb-bb..¥F-.P.b-anbrpn.p-nbbbe-bbF-nnpnbLP-Ppr » w n w w m m u. r w o i .5938 56mm.“ 30% TIME COMPRESSION IN PERCENT 28 Figure 4. Speech discrimination in percent (mean and i one standard deviation) as a function of time compression at 16 dB sensation level. '00 90 IIrIIIIUlr111tittjlifitTfiITTIIll11l|1iliiilll'Til S '5 PERCENT CORRECT l 29 l l L J 0‘7. 307. 40% 507. TIME COMPRESSION IN PERCENT 60% 70% 30 Figure 5. Speech discrimination in percent (mean and i one standard deviation) as a function of time compression at 24 dB sensation level. 31 P-bbbb-Pb-h-nPPbb-ib-P-hh-npDPP-P-DPPN-P-b-PPB-PP- m a u n a a e a ... m BmmmoopZmummm O 7074 30% 40% 50% 60% 0‘7. TIME (IMPRESSION IN PERCENT 32 Figure 6. Speech discrimination in percent (mean and i one standard deviation) as a function of time compression at 32 dB sensation level. co 3 PERCENTCDRRECT TUUITITUIIIrITIU'U‘lerrrTT‘I'TIIWTIIVII11IIITII 8 IO 33 l l l l L 0% 30'!- ‘107. 507. 60% 707. TIME (DMPRESSION IN PERCENT 34 Figure 7. Speech discrimination in percent (mean and i one standard deviation) as a function of time compression at 40 dB sensation level. PERCENT CORRECT 35 I” 90 S 8 IO O l I l L l 07. 30% 40% 50% 60% 70% TIME COMPRESSION IN PERCENT 36 Figure 8. Average articulation scores collapsed over sensation level, plotted by time compression conditions, illustrating similarities in slopes of functions between normal-hearing (Beasley, Schwimmer and Rintelmann, 1972; Beasley, Forman and Rintelmann, 1972) and sensorineural groups. 37 *3: £00 .Hzmummm 2H onmmmmazdo m2: *0.“ R0? #0» so 36033 Hansofiuomeom u $6035..." Maude: 1250: u a fl — - I J_ L l j A L L A 06 3 8 3 133212101) .LNEDHEId 8 0e 38 Figure 9. Individual subject performance in percent, as a function of time compression at 16 dB sensation level. 39 "I x—x - 2. H - o——-o 4°“ 81118 » o——-o : 0 x—---x ” .. a 0"“‘D " 0x w A I/ \\ p \ 1O.- / \\\ / \ L c/ \ \ ’ \ I . \ \ E w D . \\ \ i \ L \ I ‘0 '3 \\ r- \\ I 0‘ \ .9: O\\\ . \ r ‘0 \' : . ’sz \ : \ \ ”I . “\ \ \ I \ \ ‘ , \\ \ ”in \\\\ \ 1: \ ”’B - \\ b \\ \ ”Ju- . \\ 4.. \ o \\ D . \ . P \ \ \ 4b X \ I Io r- \ o .. x \ r \ ‘. panda 0H. .qmm mo m.oe ocflaommn ”monocmumo mm-:ne men we oncommoe zocoscoem omegahmo umoa econmhmo unwfle ...... a -- 4"- ‘- 1, . . n a . . p =2. L. < , / / oH om om ow om 105 APPENDIX E INSTRUCTIONS GIVEN TO LISTBNERS 106 You will now hear a tape recording of lists of words, each composed of fifty monosyllabic words. Each'word is preceded.by a carrier phrase, "Yen will say". Your task will be to write down the word immediately following the carrier phrase in the appropriate space provided on the answer sheet. Fer example, if you hear, "You will say dog”, you would be expected to write the word "dog”. There will be an ample amount of time provided immediately after each word presentation for you to write down your response. The lists will be presented to you at different intensity levels, although all of the fifty words on the same list will be equal- ly loud. Some of the lists may sound extremely soft, so it is of ex- treme importance that you pay careful attention to the listening task. In addition, it may seem that the words are spoken on this tape in an unusually rapid manner, so again, pay close attention to what you hear and respond to the best of your ability. If you are uncertain of a reSponse item you are encouraged to guess. When you have completed an entire word list, there will be approximately 2 minutes before the items from the next list will be presented. Are there any questions? 107 APPENDIX F ANSWER FORM USED BY LISTENERS 108 Age yrs. mos. 10 11 12 13 14 15 l6 17 18 19 20 21 22 23 24 25 Form Sex Date 26 27 28 29 3O 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 109 A APPENDIX G 4 LISTS OF FORM B NU AUDITORY TEST NO. 6 110 NORTHWESTERN UNIVERSITY AUDITORY TEST NO. 6, FORM B LIST I burn lot sub home dime which keen yes boat sure hurl door kite sell nag take fall week death love tough gap moon choice king size pool vine Chalk laud goose shout fat puff jar reach rag mode tip page raid raise bean hash limb third jail knock whip met LIST II live voice ton learn match chair deep pike room read calm book dab loaf goal shack far witch rot pick fail said wag haze white hush dead pad mill merge juice keg gin nice numb chief gaze young keep tool soap hate turn rain shawl bought thought bite lore south LIST III sheep cause rat bar mouse talk hire search luck cab rush five team pearl soup half chat road pole phone life pain base mop mess germ thin name ditch tell cool seize dodge youth hit late 1198 w1re walk date when ring check note gun beg void shall lid good LIST IV rose dog time such have mob bone sail rough dip join check wheat thumb near lease yearn kick get lose kill fit judge should pass back hall bath tire peg perch chain make long wash food mood neat tape ripe hole gas came vote lean red doll shirt sour wife 111 APPENDIX H ORDER OF PRESENTATION OF NU AUDITORY TEST NO. 6 H N NNNI—‘I—II—‘I—‘HI-‘I-J NI—IOtooouoxm-c-u 23. 24. HH Honoooxioxu-IALNNI—I TC 40 70 40 3O 50 60 70 60 50 60 30 40 40 30 60 70 50 50 30 O 0 SUbject 1 SL 24 4O 40 32 16 24 16 24 16 24 16 32 24 16 40 40 40 32 40 24 32 32 16 32 LIST II III IV II III IV III IV II IV II III II III IV II III IV H N hihih‘ own-u: NNNHHHH NHO‘OOOVO‘ 23. N .b HH HOKOOOVONm-bLNNI—‘I TC 40 50 40 4O 70 30 70 30 50 70 4O 60 60 7O 60 30 60 50 30 50 112 SUbject 2 SL 24 16 40 16 24 32 40 24 16 40 32 40 32 32 32 16 32 16 24 24 40 24 40 32 LIST I II III IV II III IV I III IV I II IV I II III I II III IV II III IV I I—II—II—II-II-I 001th H \) NNNI—‘H NHO‘OW I-II—s I—touaooucnu-IAIANH 23. N A TC 30 40 70 6O 40 40 60 30 4O 50 7O 70 50 60 70 30 50 60 30 50 SUbject 3 SL 16 4O 40 24 16 24 32 32 32 16 24 32 32 16 40 40 4O 24 4O 24 16 24 16 32 LIST II III IV II III IV III IV II IV II III II III IV II III IV OOOVOU'IALNNI—A e e o e e o o e 0 TC 30 7O 70 60 70 30 40 50 50 40 40 60 30 40 50 60 60 50 70 subject 4 SL 40 40 16 24 24 32 32 32 16 40 24 16 16 16 40 16 24 40 32 40 32 24 24 LIST II III IV II III IV III IV II IV II III II III IV II III IV H N NNHHHHHHH Hooooxloxm-bu N N 23. N A I—|I-| I—IOIoooonxcn-ALNNI-I TC 40 30 3O 40 50 60 50 60 7O 60 30 50 30 40 40 70 50 7O 70 113 subject 5 SL 32 24 40 24 24 40 32 16 40 16 40 24 16 32 32 16 16 40 40 24 24 32 32 16 LIST I II III IV II III IV I III IV I II IV I II III I II III IV II III IV I DwVO‘U'l-bLNNI-I TC 40 70 3O 60 60 30 40 50 70 70 40 50 60 50 50 30 60 30 70 40 subject 6 SL 40 40 4O 32 24 32 32 32 24 32 24 40 16 40 4O 32 16 24 16 16 16 24 16 24 LIST I II III IV II III IV I III IV I II IV I II III I II III IV II III IV I H N NNNNNHHHHHHH AWNI—AOKDOOVONU'IAM I—‘I—l HOLDOOVGU'IJiLNNI-J TC 40 70 40 7O 30 60 60 6O 30 50 70 50 60 70 40 50 30 40 50 subject 7 SL 32 24 32 40 16 32 16 16 24 32 16 32 40 40 40 16 4O 24 24 24 40 24 16 32 LIST I II III IV II III IV I III IV I 11 IV I II III I II III IV II III IV I H N HHHHI—l \lOm-D-LN O O O O O NNNI—‘H NHOKOM I O O O O O 23. N A I—AI—t HoooouoxmmeI—a O O I I O O O O O 0 . TC 60 50 70 4O 7O 40 60 50 SO 40 7O 50 40 60 70 60 30 30 114 subject 8 SL 40 40 32 32 32 16 24 32 24 24 40 24 16 16 32 24 16 40 32 24 40 16 16 40 LIST I II III IV II III IV I III IV I II IV I II III I II III IV II III IV I I—lI—II—II—II—a thI—Io'ooouoma-MNI—t H U"! NNNI—‘I—‘HH NHOKDWVO‘ O O O O O I O O 23. 24. TC 60 70 50 60 50 50 60 70 70 50 40 30 40 60 30 40 40 30 70 0 subject 9 SL 40 40 40 32 32 16 24 32 24 24 40 32 32 40 40 32 16 24 16 24 24 16 16 16 LIST I II III IV II III IV I III IV I II IV I II III I II III IV II III IV I 115 APPENDIX I TEST RESULTS OF 9 SUBJECTS 116 NNN NN.N NN.O NN NN NNN NO NN.NN NO m NNO NO NNO NO NNO NON NNO NO NNO NON NNO NNN NNO NO NOO NNN NNO NO NON OO NNO NNN NOO NO NNO NO NNO NON NNO NO NNO NON NNO NO NNO NON NOO NO NON NN NNO NON NNO NO NNO NNN NNO NO NOO NN NNO NON NNO NON NNO NON NNO NO NON ON NOO NNN NNO NO NNO NO NNO NO NNO NO NNO NON NNO NN NNO NNN NOO NO NON ON NN.NN NON NON NN.NN NNN NOO NN.ON NN.NO NN.ON m NNO NNN NNO NNN NNO NNO NNO NOO NNO NNN NNO NON NNO NNN NNO NON NNO NON NOO OO NOO NOO NNO NON NNO NNN NNO NNN NOO NON NOO NNN NOO NON NNO NNN NOO NNO NOO NN NOO NON NNO NON NNO NNN NOO NON NNO NON NNO NOO NOO NNN NNO NOO NNO NOO NOO ON NNO NNN NNO NON NOO NNN NOO NOO NOO NNN NNO NOO NNO NNN NNO NNO NNO NON NOO ON NN.NO NN.NO NNO NN ON NN OO NON NN.ON NOO NOO m NNO NON NNO NOO NNO NON NNO NOO NNO NNN NNO NNN NNO NNN NOO NON NNO NON NON OO NNO NOO NNO NON NNO NON NNO NNO NNO NNO NNO NON NNO NNN NNO NNN NNO NON NON NN NOO NNN NNO NOO NOO NOO NNO NNN NNO NNO NNO NOO NOO NON NNO NOO NNO NOO NON ON NNO NON NNO NON NNO NON NNO NNN NNO NON NOO NON NOO NON NNO NNO NNO NON NON ON NON NN.NO NON NN.NN NN.NO NN.NN NNN NN.ON NN.NO m. NNO NOO NNO NOO NOO NOO NNO NOO NNO NOO NNO NON NNO NNN NNO NNN NNO NNN NOO OO NNO NON NNO NON NNO NOO NOO NOO NNO NNO NNO NNN NNO NOO NOO NNN NNO NNN NOO NN NNO NNN NOO NON NNO NNN NNO NNN NNO NNN NNO NNN NNO NON NNO NON NNO NOO NOO ON NNO NNN NNO NNN NOO NOO NNO NON NNO NOO NOO NOO NNO NON NOO NNN NNO NOO NOO ON NNN NN.NO NNN NNO NON NN.ON NN.NO NNO NN.NN m NNO NON NNO NOO NOO NON NNO NNO NNO NOO NNO NON NNO NOO NOO NNN NNO NNN NON OO NOO NNN NNO NNO NNO NNO NNO NNO NNO NNN NNO NON NNO NOO NNO NOO NOO NNN NON NN NNO NNN NOO NNN NNO NNN NOO NON NOO NNN NOO NON NNO NOO NOO NNN NNO NNN NON ON NNO NON NOO NNN NNO NOO NNO NNO NNO NOO NNO NNN NNO NNN NNO NON NOO NNO NON ON NON NN.NO NNN NN.ON NNO NN.NN NNN NN.ON NN.NN .m NNO NON NNO NNN NNO NOO NNO NOO NNO NNO NNO NNN NNO NOO NNO NNN NNO NNO NO OO NNO NON NNO NOO NOO NON NNO NNO NOO NNO NOO NOO NNO NOO NNO NON NNO NNO NO NN NOO NNO NOO NON NNO NOO NOO NNN NNO NOO NOO NNN NNO NON NNO NOO NNO NON NO ON NNO NON NOO NOO NNO NON nOO NON NOO NON INNO NONI NOO NNO NNO NOO .NMO NON NO ON O N N O N O N N N ON NN NNmoficone NNN 565 .8935 um: 0-22 05 v.33 3035 game New EBNNN “awoken NNN 980m 533535