SOME SUGGESTIONS ON HOW A TRANSPOSER HEARING AID
TO
EVALUATE
Roy W. Gengel Gallaudet College, Washington, D. C.
Kathleen O. Foust D. C. General Hospital, Washington, D. C.
The research presented here indicates that transposer hearing aids, which are now available commercially, might be helpful to some peolJle. Specifically, it might help some people to detect t h e / s / , / S / , / t / , / t S / , and possibly/k/phonemes in speech. Any person considering the purchase of a transposer should be properly tested with one to determine whether the information provided by frequency transposition is helpful. It appears this evaluation cannot be done properly using procedures developed to evaluate a conventional hearing aid for a person with a mild or moderate communication impairment. Rather than outline a specific procedure, this report makes suggestions that a clinician might find useful when asked to evaluate the possible benefits of a transposer hearing aid for a client.
A transposer hearing aid is designed to provide additional speech information to persons who have low-frequency sensitivity but little or no sensitivity for high-frequency sounds. Johansson (1966) reported that some severely hearingimpaired children showed improved speech discrimination and speech production when trained with a transposer aid. However, Ling (1968) found no differences in performance of hearing-impaired children trained under transposer or conventional types of amplification. T h e transposer hearing aid evaluated (Johansson, 1961) was a prototype model (Oticon, T P 64) and one that is now available commercially (Oticon, T P 72). Basically, it is a two-channel system, packaged as a body-worn hearing aid. Channel One (Selector-Switch Position I) is a conventional hearing aid with a H e a r i n g Aid Industry Conference frequency range of about 150-3000 Hz. Channel T w o transposes high-frequency energy (4000-6000 Hz) into lowfrequency noise (below 1500 Hz). W h e n both channels are combined (SelectorSwitch Position II), the listener receives conventionally amplified speech plus high-frequency information, as in stop and fricative consonants, transposed into low frequencies. T h e transposer aid (Selector-Switch Position II) was compared with a con206
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GENGEL, FOUST.. TRANSPOSER HEARING AID
207
ventional aid (Position I), using hearing-impaired adults as subjects (Foust and Gengel, 1973). T h e use of adults minimized some problems inherent in working with children, such as low motivation, short attention span, and severely limited vocabulary. This report makes suggestions to clinicians who want to evaluate a transposer for a given client. Potential Candidates for Transposer Hearing Aids. Johansson (1961) indicated that his transposer aid was designed primarily for people with no hearing sensitivity above about 1500 Hz. A different criterion is suggested herein: namely, one based on whether a person has little or no auditory sensitivity for the friction sounds /s/ and /J'] and the plosive sounds It/ and ]k]. Thus people who cannot hear these sounds when speech is amplified to a comfortable level, or who hear them only occasionally or faintly, are potential candidates for transposer hearing aids. People who easily detect these sounds probably will not benefit from transposition. Special Test Materials Required. As indicated, Channel II of the transposer changes sounds in the frequency region between about 4000-6000 Hz into lower-frequency sounds. Other frequencies are unaffected. The phonemes /s/, / j ' / , / t / , a n d / t S / and to a lesser extent ]k/ are modified significantly by the transposer. These high-frequency bursts of noise are transformed into lowfrequency bursts. On the other hand, the p h o n e m e s / f / , /o/, a n d / p / o f t e n are too faint to be heard even when transposed. Therefore, words such as show, so, and toe will be modified by the transposer aid but low, row, and no will not. To establish potential candidacy for a transposer aid, it is suggested that tests be given of words or nonsense syllables such as so versus oh and she versus eat. If such distinctions can be made more easily with a transposer aid than with a conventional aid, further evaluations are probably in order. Note, however, that words such as so and show will sound almost identical and probably should not be paired. Similarly, so versus toe should not be paired since training may be required to recognize the important cue, that is, the longer duration of the noise burst in so (Pickett and Gengel, 1973). Time [or Training. Evaluations of a transposer aid probably should be done in conjunction with a training program. When the high-frequency portion of speech is modified by a transposer aid, the resultant no longer sounds like the normal speech a person received from a conventional hearing aid. High-frequency phonemes are perceived either for the first time or as having a different quality. This new situation may be confusing to an inexperienced listener. Discrimination of monosyllabic words may actually be poorer initially with the transposer than with a conventional aid (Foust and Gengel, 1973). In addition, the client may feel annoyance, frustration, or disappointment. Therefore, training and counseling should be an integral part of the evaluation of a transposer. In word discrimination tests item-by-item knowledge of results is a useful device for helping a person become accustomed to a transposer and for helping him learn to use the cues provided by it. Other forms of training such as prompting may also be effective. We suggest that any training program be flexible with an emphasis on the
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
208
JOURNAL OF SPEECH A N D HEARING DISORDERS
--
XL, 2
individual characteristics of the client's handicap. Closed-set word tests as well as open-set tests may be useful during training. Additionally these tests might be used with and without the additional cues provided by lipreading. T h e primary consideration is to choose a format that will differentiate potential distinctions between transposer and conventional amplification. T h e test should be difficult, but not so difficult as to result in near change performance; or at the other extreme, it should not be so easy as to result in near perfect performance. It probably would be wise to load the test heavily with items that might differentiate between transposer and conventional amplification. For example, if the test is not heavily loaded with items containing the phonemes /s/, /f/, / t / , / t f / , and /k/, performance with and without transposition probably will not differ even if the test format has the required degree of difficulty. In hindsight, earlier tests with modified rhyme tests were found to be poor choices for the reason just given. Client's Attitude. It has been indicated that some people initially may show negative attitudes toward transposer-amplified speech, because of its unusual character. If these negative feelings persist, it is doubtful that the person will use a transposer even if it is beneficial to him. Therefore, it is important to monitor the client's attitudes during the training period and to help him adjust to the new experience. One forceful technique to develop a positive attitude is simply to demonstrate consistently better or less effortful performance with a transposer than with a conventional aid in a discrimination test. People who benefited from transposition as indicated by test results acquired positive attitudes. In cases where test results indicated no additional benefits from transposition, people typically indicated no preference for the transposer aid. Realistic Test Situation. A real world test situation might include sentences as test materials, be conducted in noisy as well as quiet environments, and allow the client to use lipreading cues as well as cues provided by amplification. Severely hearing-impaired people often use a hearing aid as an aid to lipreading. They cannot understand many sentences by hearing alone or by seeing alone. Performance is best when both sense modalities are used together. Although experience with transposer amplification in a real world situation is limited, it is possible to make the following observations. It is very important to evaluate a transposer aid with sentence materials. For example, although one subject showed higher performance for word discrimination with transposition, she showed great confusion on a sentence test. She complained that the transposed bursts made it difficult to judge when one word ended and the next began. Obviously this person was not ready to use a transposer aid effectively. Another subject showed no additional benefit from transposition when tested with sentence materials. Nevertheless, she insisted that she exerted less listening effort with the transposer aid and preferred it to the conventional aid. This person probably would be a good candidate for a transposer aid in light of her attitude toward it and her demonstrated superior performance with it on word tests.
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
GENGEL, FOUST: TRANSPOSER HEARING AID
209
W h a t about a noisy situation? T h e transposer aid will transpose any highfrequency noise such as air turbulence in hot air heating ducts. In such an environment, a person might communicate more effectively with the transposer aid operating in its conventional mode. However, in a limited series of tests using sentence materials with a background ot voice babble (S/N = + 3 0 , + 15, 0 dB), in a combined listening-lipreading situation, subjects showed no greater decrement in performance with the transposer than with the conventional aid. O u r recommendation is to give a client listening experiences that include background noise. T h e n he can be counseled about the general effects of noise on speech communication and hopefully he can judge for himself whether communication in noise is more difficult with transposed than with conventional amplification. Clinician-Client Evaluation. In any evaluation of a transposer aid, it is a desirable practice to have both the clinician and the client listen to the speech signals, by means of a Y-cord arrangement. One arm of the Y goes to the receiver that the client uses. T h e other goes to a small amplifier-attenuator circuit and then to a receiver that the clinician uses. W i t h this arrangement, both people can listen simultaneously to the o u t p u t of the transposer aid at their individual comfortable listening levels. T h i s allows the monitoring of the transposer aid during all training and testing situations. Thus, it is always known what the aid is doing, or conversely, what it is not doing. Thus, for example, in attempting to teach an / s / versus / t / distinction, if the clinician cannot easily perceive a noise-duration cue, the client would hardly be expected to do so either. Or if the clinician does not hear a transposed [f/, the client can't be expected to do so either. Another, perhaps more subtle advantage, is that the Y-cord arrangement seems to tie the clinician and client into a closer relationship psychologically. Essentially, both people are sharing a listening experience. It is difficult to indicate how much time it probably would take to properly evaluate a transposer for a client. This is a new aid with little clinical data regarding its value. A liberal trial period is recommended offering as many training sessions as needed to adjust the client both auditorily and emotionally to the aid. At this time, it is probably best to be cautious in recommending one, except in instances where the client is obviously pleased with its performance. Nevertheless, a transposer aid seems to have potential value for some people with severe auditory communication handicaps and hopefully the experiences described here will help clinicians in properly evaluating it. ACKNOWLEDGMENT Evaluation of the transposer hearing aid was supported in part by Grant No. OEG-2-7070070-1522. The Oticon Corporation loaned the transposer hearing aids used in the project. Requests for reprints should be addressed to Roy W. Gengel, Department of Communication Disorders, University of Massachusetts, Amherst, Massachusetts 01022.
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
210
JOURNAL OF SPEECH AND HEARING DISORDERS
--
XL, 2
REFERENCES FOUST, K. O., and GENGEL, R. W., Speech discrimination by sensorineural hearing-impaired persons using a transposer hearing aid. Scand. Audiol., 2, 161-170 (1973). JO~ANSSON, B., A new coding amplifier system for the severely hard of hearing. Proc. Third Int. Congr..4coust. (Vol. II) 655-657 (1961). JOHANSSON, B., Use of the transposer for the management of the deaf child. Int..4udiol., 5, 362-372 (1966). LINc, D., Three experiments on frequency transposition. Amer. Ann. Deal 113, 283-294 (1968). PICKETT, J. M., and GENCEL, R. W., Research on frequency transposition for hearing aids. Final Report, Project No. 182071, Grant No. OEC-2-7-070070-1522 (1973). Received June 20, 1974. Accepted August 1, 1974.
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
TO
EVALUATE
Roy W. Gengel Gallaudet College, Washington, D. C.
Kathleen O. Foust D. C. General Hospital, Washington, D. C.
The research presented here indicates that transposer hearing aids, which are now available commercially, might be helpful to some peolJle. Specifically, it might help some people to detect t h e / s / , / S / , / t / , / t S / , and possibly/k/phonemes in speech. Any person considering the purchase of a transposer should be properly tested with one to determine whether the information provided by frequency transposition is helpful. It appears this evaluation cannot be done properly using procedures developed to evaluate a conventional hearing aid for a person with a mild or moderate communication impairment. Rather than outline a specific procedure, this report makes suggestions that a clinician might find useful when asked to evaluate the possible benefits of a transposer hearing aid for a client.
A transposer hearing aid is designed to provide additional speech information to persons who have low-frequency sensitivity but little or no sensitivity for high-frequency sounds. Johansson (1966) reported that some severely hearingimpaired children showed improved speech discrimination and speech production when trained with a transposer aid. However, Ling (1968) found no differences in performance of hearing-impaired children trained under transposer or conventional types of amplification. T h e transposer hearing aid evaluated (Johansson, 1961) was a prototype model (Oticon, T P 64) and one that is now available commercially (Oticon, T P 72). Basically, it is a two-channel system, packaged as a body-worn hearing aid. Channel One (Selector-Switch Position I) is a conventional hearing aid with a H e a r i n g Aid Industry Conference frequency range of about 150-3000 Hz. Channel T w o transposes high-frequency energy (4000-6000 Hz) into lowfrequency noise (below 1500 Hz). W h e n both channels are combined (SelectorSwitch Position II), the listener receives conventionally amplified speech plus high-frequency information, as in stop and fricative consonants, transposed into low frequencies. T h e transposer aid (Selector-Switch Position II) was compared with a con206
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
GENGEL, FOUST.. TRANSPOSER HEARING AID
207
ventional aid (Position I), using hearing-impaired adults as subjects (Foust and Gengel, 1973). T h e use of adults minimized some problems inherent in working with children, such as low motivation, short attention span, and severely limited vocabulary. This report makes suggestions to clinicians who want to evaluate a transposer for a given client. Potential Candidates for Transposer Hearing Aids. Johansson (1961) indicated that his transposer aid was designed primarily for people with no hearing sensitivity above about 1500 Hz. A different criterion is suggested herein: namely, one based on whether a person has little or no auditory sensitivity for the friction sounds /s/ and /J'] and the plosive sounds It/ and ]k]. Thus people who cannot hear these sounds when speech is amplified to a comfortable level, or who hear them only occasionally or faintly, are potential candidates for transposer hearing aids. People who easily detect these sounds probably will not benefit from transposition. Special Test Materials Required. As indicated, Channel II of the transposer changes sounds in the frequency region between about 4000-6000 Hz into lower-frequency sounds. Other frequencies are unaffected. The phonemes /s/, / j ' / , / t / , a n d / t S / and to a lesser extent ]k/ are modified significantly by the transposer. These high-frequency bursts of noise are transformed into lowfrequency bursts. On the other hand, the p h o n e m e s / f / , /o/, a n d / p / o f t e n are too faint to be heard even when transposed. Therefore, words such as show, so, and toe will be modified by the transposer aid but low, row, and no will not. To establish potential candidacy for a transposer aid, it is suggested that tests be given of words or nonsense syllables such as so versus oh and she versus eat. If such distinctions can be made more easily with a transposer aid than with a conventional aid, further evaluations are probably in order. Note, however, that words such as so and show will sound almost identical and probably should not be paired. Similarly, so versus toe should not be paired since training may be required to recognize the important cue, that is, the longer duration of the noise burst in so (Pickett and Gengel, 1973). Time [or Training. Evaluations of a transposer aid probably should be done in conjunction with a training program. When the high-frequency portion of speech is modified by a transposer aid, the resultant no longer sounds like the normal speech a person received from a conventional hearing aid. High-frequency phonemes are perceived either for the first time or as having a different quality. This new situation may be confusing to an inexperienced listener. Discrimination of monosyllabic words may actually be poorer initially with the transposer than with a conventional aid (Foust and Gengel, 1973). In addition, the client may feel annoyance, frustration, or disappointment. Therefore, training and counseling should be an integral part of the evaluation of a transposer. In word discrimination tests item-by-item knowledge of results is a useful device for helping a person become accustomed to a transposer and for helping him learn to use the cues provided by it. Other forms of training such as prompting may also be effective. We suggest that any training program be flexible with an emphasis on the
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
208
JOURNAL OF SPEECH A N D HEARING DISORDERS
--
XL, 2
individual characteristics of the client's handicap. Closed-set word tests as well as open-set tests may be useful during training. Additionally these tests might be used with and without the additional cues provided by lipreading. T h e primary consideration is to choose a format that will differentiate potential distinctions between transposer and conventional amplification. T h e test should be difficult, but not so difficult as to result in near change performance; or at the other extreme, it should not be so easy as to result in near perfect performance. It probably would be wise to load the test heavily with items that might differentiate between transposer and conventional amplification. For example, if the test is not heavily loaded with items containing the phonemes /s/, /f/, / t / , / t f / , and /k/, performance with and without transposition probably will not differ even if the test format has the required degree of difficulty. In hindsight, earlier tests with modified rhyme tests were found to be poor choices for the reason just given. Client's Attitude. It has been indicated that some people initially may show negative attitudes toward transposer-amplified speech, because of its unusual character. If these negative feelings persist, it is doubtful that the person will use a transposer even if it is beneficial to him. Therefore, it is important to monitor the client's attitudes during the training period and to help him adjust to the new experience. One forceful technique to develop a positive attitude is simply to demonstrate consistently better or less effortful performance with a transposer than with a conventional aid in a discrimination test. People who benefited from transposition as indicated by test results acquired positive attitudes. In cases where test results indicated no additional benefits from transposition, people typically indicated no preference for the transposer aid. Realistic Test Situation. A real world test situation might include sentences as test materials, be conducted in noisy as well as quiet environments, and allow the client to use lipreading cues as well as cues provided by amplification. Severely hearing-impaired people often use a hearing aid as an aid to lipreading. They cannot understand many sentences by hearing alone or by seeing alone. Performance is best when both sense modalities are used together. Although experience with transposer amplification in a real world situation is limited, it is possible to make the following observations. It is very important to evaluate a transposer aid with sentence materials. For example, although one subject showed higher performance for word discrimination with transposition, she showed great confusion on a sentence test. She complained that the transposed bursts made it difficult to judge when one word ended and the next began. Obviously this person was not ready to use a transposer aid effectively. Another subject showed no additional benefit from transposition when tested with sentence materials. Nevertheless, she insisted that she exerted less listening effort with the transposer aid and preferred it to the conventional aid. This person probably would be a good candidate for a transposer aid in light of her attitude toward it and her demonstrated superior performance with it on word tests.
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
GENGEL, FOUST: TRANSPOSER HEARING AID
209
W h a t about a noisy situation? T h e transposer aid will transpose any highfrequency noise such as air turbulence in hot air heating ducts. In such an environment, a person might communicate more effectively with the transposer aid operating in its conventional mode. However, in a limited series of tests using sentence materials with a background ot voice babble (S/N = + 3 0 , + 15, 0 dB), in a combined listening-lipreading situation, subjects showed no greater decrement in performance with the transposer than with the conventional aid. O u r recommendation is to give a client listening experiences that include background noise. T h e n he can be counseled about the general effects of noise on speech communication and hopefully he can judge for himself whether communication in noise is more difficult with transposed than with conventional amplification. Clinician-Client Evaluation. In any evaluation of a transposer aid, it is a desirable practice to have both the clinician and the client listen to the speech signals, by means of a Y-cord arrangement. One arm of the Y goes to the receiver that the client uses. T h e other goes to a small amplifier-attenuator circuit and then to a receiver that the clinician uses. W i t h this arrangement, both people can listen simultaneously to the o u t p u t of the transposer aid at their individual comfortable listening levels. T h i s allows the monitoring of the transposer aid during all training and testing situations. Thus, it is always known what the aid is doing, or conversely, what it is not doing. Thus, for example, in attempting to teach an / s / versus / t / distinction, if the clinician cannot easily perceive a noise-duration cue, the client would hardly be expected to do so either. Or if the clinician does not hear a transposed [f/, the client can't be expected to do so either. Another, perhaps more subtle advantage, is that the Y-cord arrangement seems to tie the clinician and client into a closer relationship psychologically. Essentially, both people are sharing a listening experience. It is difficult to indicate how much time it probably would take to properly evaluate a transposer for a client. This is a new aid with little clinical data regarding its value. A liberal trial period is recommended offering as many training sessions as needed to adjust the client both auditorily and emotionally to the aid. At this time, it is probably best to be cautious in recommending one, except in instances where the client is obviously pleased with its performance. Nevertheless, a transposer aid seems to have potential value for some people with severe auditory communication handicaps and hopefully the experiences described here will help clinicians in properly evaluating it. ACKNOWLEDGMENT Evaluation of the transposer hearing aid was supported in part by Grant No. OEG-2-7070070-1522. The Oticon Corporation loaned the transposer hearing aids used in the project. Requests for reprints should be addressed to Roy W. Gengel, Department of Communication Disorders, University of Massachusetts, Amherst, Massachusetts 01022.
Downloaded From: https://jshd.pubs.asha.org/ by a University of Texas, Austin User on 03/27/2018 Terms of Use: https://pubs.asha.org/ss/rights_and_permissions.aspx
210
JOURNAL OF SPEECH AND HEARING DISORDERS
--
XL, 2
REFERENCES FOUST, K. O., and GENGEL, R. W., Speech discrimination by sensorineural hearing-impaired persons using a transposer hearing aid. Scand. Audiol., 2, 161-170 (1973). JO~ANSSON, B., A new coding amplifier system for the severely hard of hearing. Proc. Third Int. Congr..4coust. (Vol. II) 655-657 (1961). JOHANSSON, B., Use of the transposer for the management of the deaf child. Int..4udiol., 5, 362-372 (1966). LINc, D., Three experiments on frequency transposition. Amer. Ann. Deal 113, 283-294 (1968). PICKETT, J. M., and GENCEL, R. W., Research on frequency transposition for hearing aids. Final Report, Project No. 182071, Grant No. OEC-2-7-070070-1522 (1973). Received June 20, 1974. Accepted August 1, 1974.
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