Journal of Rehabilitation Research and Development VOL. 30 NO. 3 1993 Accesion For / " NTIS CRAMI [ DTIC TAB E Unannounced E DTIC QUALITY INSPECteD B Justification Distribution I Avdddability Codes Avail and I or Dist Special For sale by: Superintendent of Documents, U.S. Government Printing Office (GPO) Washington, DC 20402. Available in microfilm from University Microfilms International, Inc. Indexed by: N Engineering Index (Bioengineering Abstracts) U Excerpta Medica 41 Index Medicus N The BLDOC System (French) * Index to U.S. Government Periodicals (Infordata Int., Inc.) E Social Science Index, WILSONDISC Databases (H.W. Wilson Co.) * SPORT Database / SPORT Discus (Canadian) Library of Congres Catalog Card No. 6.60273 ISSN 0007-506X The Journal of Rehabilitation Research and Development is a quarterly publication of the Rehabilitation Research and Development Service, Department of Veterans Affairs. 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They should be 103 South Gay Street - 5th floor typed separately, double-spaced, and numbered consecutively in the Baltimore, MD 21202-4051 order in which they are first mentioned in the text, with only one Telephone: (410)962-1800 reference per number. The number appropriate to each reference should Fax: (410)962-9670 H DVeeptearratnms eAnft foaifrs Journal of Rehabilitation Research and Development Volume 30, Number 3, 1993 The Journal of Rehabilitation Research and Development is a publication of the Rehabilitation Research and Development Service, Scientific and Technical Publications Section, Veterans Health Administration, Department of Veterans Affairs, Baltimore, MD EDITORIAL BOARD John W. Goldschmidt, M.D., Chairperson EDITOR Peter Axelson, M.S.M.E. Tamara T. Sowell Joseph E. Binard, M.D., F.R.C.S.(C) Bruce B. Blasch, Ph.D. Clifford E. Brubaker, Ph.D. FOREIGN EDITORS Ernest M. Burgess, M.D. Dudley S. Childress, Ph.D. Satoshi Ueda, M.D. Franklyn K. Coombs Professor, Director Charles H. Dankmeyer, Jr., C.P.O. Central Rehabilitation Service William R. De I'Aune, Ph.D. University of Tokyo Hospital Carlo J. De Luca, Ph.D. 731 Hongo, Bunkyo Joan Edelstein, M.A., P.T. Tokyo, Japan Martin Ferguson-Petl, Ph.D. Roger M. Glaser, Ph.D. Seishi Sawamura, M.D. Douglas A. Hobson, Ph.D. Director J. Lawrence Katz, Ph.D. Hyogo Rehabilitation Center H.R. Lehneis, Ph.D., C.P.O. 1070 Akebono-Cho (Tarumi-Ki) Harry Levitt, Ph.D. Kobe, 673 Japan Heinz I. Lippmann, M.D., F.A.C.P. Robert W. Mann, Sc.D. CONSULTANTS Colin A. McLaurin, Sc.D. Donald R. McNeal, Ph.D. Jacquelin Perry, M.D., Medical Consultant Paul R. Meyer, Jr., M.D. Michael J. Rosen, Ph.D., ScientifIc Consultant Jacquelin Perry, M.D. Leon Bennett, Technical Consultant Charles H. Pritham, C.P.O. James B. Reswick, Sc.D. Jerome D. Schein, Ph.D. PRODUCTION STAFF Sheldon Simon, M.D. Terry Supan, C.P.O. Ruth A. Waters, Senior Technical PublicationsE ditor Gregg C. Vanderheiden, Ph.D. Barbara G. Sambol, Technical PublicationsE ditor Peter S. Walker, Ph.D. June R. Terry, Program Assistant C. Gerald Warren Celeste Anderson, Secretary Marcia Nealey, Program Clerk INFORMATION RESOURCE UNIT Frank L. Vanni, Visual Information Specialist Nick Lancaster, Scientiric and Technical Photographer SCIENTIFIC AND TECHNICAL PUBLICATIONS SECTION MANAGEMENT Jon Peters, Acting ProgramM anager Renee Bulluck, Secretary Department of Veterans Affairs Journal of Rehablitation Research and Development Vol. 30, No. 3 1993 CONTENTS vi Guest Editorial Harry Levitt, PhD ix Clinical Relevance for the Veteran: Summaries of Scientific/Technical Articles Harry Levitt, PhD ScIentifc/Technical Artldes 297 On the evaluation of a new generation of hearing aids Robyn M. Cox, PhD 305 Preferred frequency responce for two- and three-channel amplification systems Donald D. Dirks, PhD; Jayne Ah/strom, MS; P. Douglas Noffainger, PhD 318 Do adaptive frequency response (AFR) hearing aids reduce 'upward spread' of masking? David A. Fabry, PhD; Marjorie R. Leek, PhD; Brian E. Walden, PhD; Mary Cord, MA 326 Effects of prolonged lack of amplification on speech-recognition performance: Preliminary findings Shlomo Si/man, PhD; CarolA . Silverman, PhD; Michele B. Emmer, MS; Stanley A. Gefeand, PhD 333 High-frequency testing techniques and instrumentation for early detection of ototoxicity Stephen A. Fausti, PhD; Richard H. Frey, BS; James A. Henry; MS; Deanna J. Olson, MS; Heidi I. Schaffer, MA CinIcal Report 342 Development and Use of Auditory Compact Discs in Auditory Evaluation Richard H. Wilson, PhD Departments 352 Abstracts of Recent Literature 362 Publications of Interest Joan E. Edelstein, MA, PT 378 Calendar of Events 359 Book Reviews Jerome D. Schein, PhD V GUEST EDITORIAL This issue of the Journalo f Rehabilitation Research and Development focuses on the evaluation of modern hearing aids, related devices and other technological developments. Recent technological advances have brought about substantial changes in the design of these instruments. Many modern hearing aids use digital tech, iques for controlling and processing the signals being amplified. These instruments have significant new capabilities in terms of both their signal-processing capabilities and the flexibility with which they can be prescribed and fitted. Similarly, the test instruments used for hearing-aid evaluation and audiological testing, in general, have improved substantially over the past few years with the increasing use of digital signal processing technology. The scope of these technological advances and their potential for providing improved amplification for veterans with hearing loss were addressed in Vol. 30, No. 1, 1993, of the Journal,a special issue entitled Part I: Advanced Hearing Aid Technology. This issue, Part I1: Clinical Evaluation of New Generation Hearing Aids is concerned with the evaluation of modern hearing aids embodying this new technology as well as with related issues involving hearing aids and modern test instruments. The first paper in this collection, by R.M. Cox, addresses a growing problem in the prescriptive fitting of modern hearing aids. Traditional evaluation and fitting procedures are not adequate for many modern hearing aids because of differences in the way signals are amplified and concomitant differences in the way these instruments need to be adjusted. This paper reviews the issues involved and identifies new techniques which can be used to make full use of the new capabilities of such devices. Increasing use is being made of more than one channel of amplification in the new generation of hearing aids. This basic change in hearing-aid design results in instruments of considerably greater flexibility which can be prescribed more accurately and which can deal more effectively with unfriendly acoustic environments, such as speech produced in a noisy room. The increased flexibility and the many different adjustments that are needed, however, also add to the audiologist's task in evaluating and fitting these devices. The second paper, by D. Dirks, J. Ahlstrom, and P.D. Noffsinger, is concerned with the specific problem of determining the preferred frequency-gain response of a hearing aid with two or three channels of amplification, this being the most common form of multichannel amplification being used in modern hearing aids. The results of this investigation provide a scientific basis for the development of practical prescriptive fitting strategies for hearing aids of this type. One of the most common complaints of hearing-aid users is that speech is particularly difficult to understand in the presence of background noise. Reducing the effects of background noise is a major problem in many scientific fields and a variety of techniques have been developed for this purpose, many of which require extensive signal processing. There are, however, inherent limitations on how much noise can be eliminated even with the most advanced signal processing techniques. The third paper, by D.A. Fabry, M.R. Leek, B.E. Walden, and M. Cord, evaluates a form of noise reduction that has been incorporated in several modern hearing aids. The method employed is to filter out low-frequency components of the signals being amplified when intense low-frequency noise is present. Since this filtering operation also eliminates low-frequency components of the speech signal, it is only used when low-frequency noise is present. The results of the investigation showed that for hearing losses that increase rapidly above 1,000 Hz, some improvement in speech recognition was obtained when intense (85dB SPL) rather than moderate (70dB SPL) low-frequency noise was present. Although hearing aids are among the most widely used forms of assistive technology, only a small proportion of people (including veterans) who would benefit from acoustic amplification actually use hearing aids. The fourth paper by S. Silman, C.A. Silverman, M.B. Emmer, and S.A. Gelfand, shows that for an impaired ear, lack of amplification over prolonged periods of time can result in a deterioration in speech recognition ability when amplification is finally provided. There is also evidence that speech recognition ability improves to some extent with long-term use of a VA VIi Joumal of Rehabiltation Research and Development Vol. 30 No. 3 1993 hearing aid. This is a particularly important finding with significant implications for veterans who have a hearing loss but do not use hearing aids. There have been many dramatic advances in modern medicine; these include the development of potent antibiotic drugs and new methods of intervention such as chemotherapy, which have saved many lives. Unfortunately, some of these therapeutic drugs and chemotherapeutic agents can have adverse side effects, such as ototoxicity resulting in severe hearing damage. It is thus crucial to develop efficient techniques for the early detection of hearing loss resulting from medication of this type. The fifth paper, by S.A. Fausti, R.H. Frey, J.A. Henry, D.J. Olson, and H.I. Schaffer, describes the use of high-frequency audiometry and computerized measurement of the auditory brainstem response as a means of monitoring hearing in patients at risk for hearing loss. Hearing thresholds were measured over a wide frequency range and the predictive power of these measurements in detecting possible hearing damage was evaluated. Efficient procedures for monitoring the hearing of patients receiving potentially ototoxic medication were then developed based on the results of this study. The field of automatic speech recognition has made dramatic advances in the past few years and it is hoped that the technology developed for this purpose will also be of benefit to veterans and others with severe hearing losses. The last paper in this issue falls in the Clinical Report section of the Journal dedicated to recent clinical advances. The clinical report, by R.H. Wilson, describes the development of a set of test materials on compact disc designed for use in VA Audiology Clinics. Two sets of test materials have been prepared, one for basic auditory evaluations and one for a more detailed assessment of central auditory processing. The compact disc is perhaps the most well-known product resulting from the application of digital techniques to audio engineering. The quality of a digital audio recording on compact disc is far superior to a traditional analog recording (e.g., a long-playing record), in terms of bandwidth, low distortion, and wide dynamic range. In addition, a large number of recordings can be stored on a single compact disc and individual recordings can be retrieved for playback efficiently, conveniently and, if necessary, automatically. The papers in this collection provide substantive new information that will do much to improve the quality of life of veterans with hearing loss, or at risk for hearing loss. These research results will also fill important gaps in our knowledge and be of value to the field of acoustic amplification in general. It is with some pride that we note that five of the six papers in this important collection were supported by funds from the Rehabilitation Research and Development Service of the Department of Veterans Affairs. Harry Levitt, Ph.D. Center for Research in Speech and Hearing Sciences City University of New York Allen E. Boysen, Ph.D. Director, Audiology and Speech Pathology Service Department of Veterans Affairs Guest Editors Clinical Relevance for the Veteran,; SUMMARY OF SCIENTIFIC/TECHNICAL Purpose of the Work. Hearing aids have recently PAPERS IN THIS ISSUE been developed that provide more than one channel of amplification, each channel amplifying a differ- by Harry Levitt, PhD, Guest Editor ent band of frequencies. The purpose of this investigation was to compare the preferred frequen- cy-gain responses of hearing aids with two and three channels of amplification. Subjects and Procedures. Nine subjects with mild to moderately-severe On the Evaluation of a New Generation of Hearing sensorineural hearing loss participated. Three sub- Aids. Robyn M. Cox, PhD (p. 297) jects had hearing loss that increased gradually with frequency, four subjects had hearing loss that Purpose of the Work. A new generation of hearing increased rapidly with frequency, and two subjects aids is being developed which offer the promise of had hearing loss that did not vary significantly with novel speech processing capabilities and methods of frequency. Each subject listened to continuous automatic loudness control. Fitting and evaluation speech through a computer-simulated hearing aid strategies for these new instruments are likely to and provided judgments of relative preference as the differ from those currently used for traditional hearing aid was adjusted. A statistically efficient linear hearing aids. This paper reviews the issues adjustment procedure was used under computer involved in order to develop fitting and evaluation control. Results. The three-channel system provided procedures appropriate for use with this new gener- greater flexibility in the choice of bandwidths for ation of hearing aids. Procedures. The problems amplification, but no significant differences were inherent in hearing aid evaluation are reviewed and observed between the preferred frequency-gain re- specific ways of addressing these problems are sponses that were obtained, on the average, for the described. Procedures appropriate for hearing aids two- and three-channel systems. Both systems, how- that have advanced signal processing capabilities are ever, showed a range of preferred frequency-gain identified. These include several new tests developed responses depending on the bandwidths selected for by the authors. Of particular concern are perfor- each channel. The three-channel system showed a mance evaluations in the field; the relative merits of greater spread in the choice of preferred frequency- different approaches to this problem are discussed. gain characteristics. Relevance to Veteran Popula- Results. Techniques have been identified which will tion. Many technologically advanced hearing aids avoid the pitfalls of traditional methods of hearing use more than one channel of amplification. This aid fitting and evaluation. These include several new paper provides information on the relative differ- techniques developed by the authors for evaluating ences between two- and three-channel systems in hearing aid benefit in everyday environments and determining preferred frequency-gain responses. In- for measuring relevant audiological characteristics formation of this type is needed in order to develop of the listener. Relevance to Veteran Population. more effective multichannel hearing aids and im- Modern hearing aids with new technological features proved methods of prescribing these hearing aids. are being fitted to veterans on a substantial scale. It is important that clinicians use fitting and evaluation Do Adaptive Frequency Response (AFR) Hearing procedures appropriate for these new instruments. Aids Reduce 'Upward Spread' of Masking? David A. Fabry, PhD; Marjorie R. Leek, PhD; Preferred Frequency Response for Two- and Brian E. Walden, PhD; Mary Cord, MA (p. 318) Three-Channel Amplification Systems. Donald Dirks, PhD; Jayne Ahlstrom, MS; Purpose of the Work. One approach to the problem P. Douglas Noffsinger, PhD (p. 305) of background noise in acoustic amplification is to reduce the gain at low frequencies when intense low- ix X Journal of Rehabltation Rueawch and Development Vol. 30 No. 3 1993 frequency noise is present. This technique has been Purpose of the Work. Several recent studies have used in several modern hearing aids with mixed shown that lack of amplification in an impaired ear results. This paper investigated whether a high over a prolonged period of time can result in quality hearing aid of this type (e.g., noise and decreased speech recognition ability for that ear. distortion generated internally by the instrument The purpose of this study was to investigate the itself were negligible) could produce significant im- effects of lack of amplification to the unaided ear in provements in speech recognition at high noise levels adults with a symmetric binaural hearing loss who and whether such improvements could be related to have been fitted with a monaural hearing aid. A upward spread of masking, an effect in which second objective was to investigate the effect of intense low-frequency sound reduces the audibility amplification on speech recognition performance in of high-frequency sounds. Subjects and Procedures. the aided ears of persons fitted with either monaural Eight adults with sensorineural hearing losses that or binaural hearing aids. Subjects and Procedures. increased rapidly with frequency in the region Forty-seven adults with symmetric binaural hearing between 1,000 and 2,000 Hz participated. Four loss were fitted with hearing aids; 19 were fitted adults with normal hearing also participated. The monaurally and 28 binaurally. An additional 19 masking effect of low-frequency noise at two levels normal-hearing adults served as controls. Three (moderate and intense) was measured in each sub- speech recognition tests were administered to each ject. Speech recognition scores were obtained for subject 6-12 weeks after hearing aid fitting and each noise level under two conditions of amplifica- again approximately one year later. Results. For the tion, with and without attenuation of the low subjects fitted with a monaural hearing aid, the frequencies. This attenuation was applied equally to difference in speech recognition test scores between both speech and noise, as would occur in a hearing the aided and unaided ears was found to change aid of this type. Results. The more intense low- significantly after one year of hearing-aid use. The frequency noise produced more masking in the high unaided ear showed a small reduction in test score frequencies than the less intense noise. For five of while the aided ear showed some evidence of an the eight test subjects, attenuation of the low increase in test score. No significant differences were frequencies reduced this upward spread of masking observed over the same time period for either the substantially. This reduction in high-frequency binaurally aided subjects or the normal-hearing masking was reflected in the speech recognition controls. Relevance to Veteran Population. The data scores. Attenuation of the low frequencies produced obtained in this study indicate that lack of amplifi a small increase in speech recognition for the cation in one ear can lead to poorer spee,.h low-intensity noise but a relatively large increase in recognition over time for that ear while the ear that intelligibility for the high-intensity noise. Relevance is amplified might also show a small improvement in to Veteran Population. Amplification of back- speech recognition over time. An important implica- ground noise is a particularly troublesome problem tion of this finding is that veterans with hearing for hearing-aid users. Given the large number of losses requiring amplification should be fitted with veterans who wear hearing aids, this is a problem of hearing aids as soon as possible so as to avoid great concern. The method of noise reduction further deterioration in speech reception skills re- investigated in this study provides some alleviation suiting from prolonged lack of amplification. of this problem under certain conditions (steep high-frequency hearing loss, intense low-frequency High-Frequency (8-20 kHz) Testing Techniques and noise, and a hearing aid that does not produce Instrumentation for Early Detection of Ototoxicity. significant internal noise or distortion). Stephen A. Fausti, PhD; Richard H. Frey, BS; James A. Henry, MS; Deanna J. Olson, MS; Heidi I. Schaffer, MA (p. 333) Effects of Prolonged Lack of Amplification on Speech-Recognition Performance: Preliminary Purpose of the Work. Veteran patients with certain Findings. Shlomo Silman, PhD; types of serious illnesses are often treated with Carol A. Silverman, PhD; Michele B. Emmer, MS; therapeutic drugs which have the potential of caus- Stanley A. Gelfand, PhD (p. 326) ing hearing loss. Since many of these patients