Bone-conducted Ultrasonic Hearing Aid Research Articles

Propagation characteristics of amplitude-modulated bone-conducted ultrasound presented to the neck, trunk and arms

Bone-conducted ultrasound (BCU) is perceived even by the profoundly hearing impaired and a novel hearing aid has been developed. In the BCU hearing aid, the ultrasonic carrier is amplitude-modulated by speech signals and presented to the mastoid process of the temporal bone by a vibrator. However, BCU presented to parts of the body distant from the head can be perceived. In this study, vibration at the external auditory meatus was measured when amplitude-modulated BCU was presented to distal parts of the body. The results showed spectrum peaks corresponding to the carrier frequency (30 kHz) and the modulation frequency. The peak level of the carrier frequency tended to decrease depending on the distance between the external auditory meatus and the stimulation part basically. On the other hand, the peak level of the modulation frequency did not change with the distance between the external auditory meatus and the stimulation part, whereas the effect of modulation frequency was significant.

Temporal window of integration estimated by omission in bone-conducted ultrasound

Bone-conducted ultrasound (BCU) can be heard for both normal-hearing and some profoundly deaf individuals. Moreover, amplitude-modulated BCU can transmit the speech signal. These characteristics of BCU provide the possibility of the developing a bone-conducted ultrasonic hearing aid. Previous studies on the perception mechanism of speech-modulated BCU have pointed to the importance of temporal rather than frequency information. In order to elucidate the perception of speech-modulated BCU, further investigation is need concerning the processing of temporal information. The temporal processing of air-conducted audible sounds (ACASs) involves the integration of closely presented sounds into a single information unit. The long-temporal window of integration was estimated approximately 150–200 ms, which contribute to the discrimination of speech sound. The present study investigated the long-temporal integration system for BCU evaluated by stimulus omission using magnetoencephalography.Eight participants with normal hearing took part in this study. Ultrasonic tone burst with the duration of 50 ms and frequency of 30 kHz was used as the standard stimulus and presented with steady onset-to-onset times or stimulus-onset asynchronies (SOAs). In each sequence, the duration of the SOAs were set to 100, 125, 150, 175, 200, or 350 ms. For deviant, tones were randomly omitted from the stimulus train. Definite mismatch fields were elicited by sound omission in the stimulus train with an SOA of 100–150 ms, but weren’t with an SOA of 200 and 350 ms for all participants.We found that stimulus train for BCUs can be integrated within a temporal window of integration with an SOA of 100–150 ms, but are regarded as a separate event when the SOA is 200 or 350 ms in duration. Therefore, we demonstrated that the long-temporal window of integration for BCUs estimated by omission was 150–200 ms, which was similar to that for ACAS (Yabe et al. NeuroReport 8 (1997) 1971–1974 and Psychophysiology. 35 (1998) 615–619). These findings contribute to the elucidation and improvement of the perception of speech-modulated BCU.

1J2-3 Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Assessments of the Modulation Type with Regard to Monosyllable Articulation and Confusion Analyses

1J2-3 Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Assessments of the Modulation Type with Regard to Monosyllable Articulation and Confusion Analyses

Assessments of basic properties of distal-presented bone-conducted ultrasonic hearing.

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf and a novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid) has been developed. In the BCU hearing aid, the vibrator is pressed onto a part of the cranial bone behind the ear (mastoid process). However, BCU can be heard on distal parts of the body; i. e., the muscle of the neck, the clavicle, and the upper limb. In this study, to assess basic properties of such distal-presented BCU hearing, hearing thresholds were measured when 30-kHz tone bursts were presented to the neck and the upper and lower arms in normal hearing participants. Further, to assess the basic capability of transferring information by the distal-presented BCU hearing, temporal modulation transfer functions (TMTFs), that reflect the temporal resolution of the hearing, were estimated for 30-kHz carrier. The results showed that BCUs presented to the distal parts, including the lower arm, can be perceived at least in the normal hearing, whereas threshold increased depending on the distance from the head. Also, the temporal resolutions of the distal-presented BCU hearing at the neck, and the upper and lower arms were comparable to that of the mastoid process of the temporal bone. These results provide useful information not only for the improvement of the existing BCU hearing aid, but also for the development of novel distal-presented BCU devices that can provide sound information selectively to the specific person who touches the device by the arms or so.

1P5-9 Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf : Assessments of the Modulation Type with Regard to Monosyllable Articulation and Confusion Analyses(Poster Session)

1P5-9 Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf : Assessments of the Modulation Type with Regard to Monosyllable Articulation and Confusion Analyses(Poster Session)

Development of a Bone-Conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Evaluation of Sound Quality Using a Semantic Differential Method

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. A novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid: BCUHA) has been developed. However, there is room for improvement particularly in terms of sound quality. BCU speech is accompanied by a strong high-pitched tone and contain some distortion. In this study, the sound quality of BCU speech with several types of amplitude modulation [double-sideband with transmitted carrier (DSB-TC), double-sideband with suppressed carrier (DSB-SC), and transposed modulations] and air-conducted (AC) speech was quantitatively evaluated using semantic differential and factor analysis. The results showed that all the types of BCU speech had higher metallic and lower esthetic factor scores than AC speech. On the other hand, transposed speech was closer than the other types of BCU speech to AC speech generally; the transposed speech showed a higher powerfulness factor score than the other types of BCU speech and a higher esthetic factor score than DSB-SC speech. These results provide useful information for further development of the BCUHA.

Speech intelligibility of hearing impaired participants in long-term training of bone-conducted ultrasonic hearing aid

Bone-conducted ultrasonic hearing aid (BCUHA) system is the unique device to provide the auditory sensation to profoundly hearing-impaired persons without any surgical operations. To clarify effects of long-term hearing training with this device, two deaf participants engaged the BCUHA training for 9 months. They were trained to use BCUHA through repetition of sentences read aloud and free conversation, and then they took part in word recognition tests and monosyllabic identification tests. Both participants showed that they could recognize words above chance using auditory sensation only provided by BCUHA device if alternatives or context were presented to them during the trials. Besides, it was observed that monosyllabic intelligibility score with both of auditory and visual cue had much increased with the day of training than the score with auditory cue only and that with visual cue only. The result suggests that the long-term training with BCUHA achieves efficient integration of auditory and visual cue of speech such as cochlear implant users showed in previous studies.

Evaluation of bone-conducted ultrasonic hearing-aid regarding transmission of phonetic features

Human listeners can perceive speech signals in a voice modulated ultrasonic carrier from a bone-conduction stimulator, even if the listeners are patients with sensorineural hearing loss. Considering this fact, we have been developing a bone-conducted ultrasonic hearing aid (BCUHA). The purpose of this study is to evaluate the ability of BCUHA to transmit Japanese distinctive features to the recipient. For this purpose, a series of mono-syllable intelligibility experiments was conducted. A series of sequential information transfer analyses (SINFA) were carried out to analyze what kind of articulatory features were well transmitted. Results of the SINFA showed that: in vowel perception, “openness” and “frontness” were well transmitted, while in consonant perception, Japanese “you-on” (palatalized sound) feature was well transmitted; however, transmission of other features like articulatory position or manner was limited. These results indicated that the BCUHA has sufficient frequency resolution to transmit vowel information, while some signals are masked by carrier sound. To improve this problem, further investigation and development is required.

Development of a novel hearing-aid for the profoundly deaf using bone-conducted ultrasonic perception: Assessments of the modulation type with regard to articulation, intelligibility, and sound quality

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. We have developed a novel hearing-aid using BCU perception (BCU hearing aid: BCUHA) for the profoundly deaf. In the BCUHA, ultrasonic sinusoids of about 30 kHz are amplitude-modulated by speech and presented to the mastoid. Generally, two sounds are perceived: one is a high-pitched tone due to the ultrasonic carrier, with a pitch corresponding to a 8–16 kHz air-conducted (AC) sinusoid, and the other is the envelope of the modulated signal. As a method of amplitude modulation (AM), double-sideband with transmitted carrier (DSB-TC) modulation had been used; however, the DSB-TC is accompanied by a strong high-pitched tone. In this study, two new AM methods, double-sideband with suppressed carrier (DSB-SC) and transposed modulation (TM), that can be expected to reduce the high-pitched tone were newly employed in the BCUHA, and their resulting articulations, intelligibilities, and sound qualities were evaluated. The results showed that DSB-TC and TM had higher articulation and intelligibility scores than DSB-SC. Further, in terms of sound quality, the TM speech was closer than other types of BCU speech to AC speech. These results provide useful information for further development of the BCUHA.

Development of Bone-Conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Assessments of the Modulation Type with Regard to Intelligibility and Sound Quality

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. A novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid: BCUHA) has been developed; however, further improvements are needed, especially in terms of articulation and sound quality. In this study, the intelligibility and sound quality of BCU speech with several types of amplitude modulation [double-sideband with transmitted carrier (DSB-TC), double-sideband with suppressed carrier (DSB-SC), and transposed modulation] were evaluated. The results showed that DSB-TC and transposed speech were more intelligible than DSB-SC speech, and transposed speech was closer than the other types of BCU speech to air-conducted speech in terms of sound quality. These results provide useful information for further development of the BCUHA.

Development of Bone-Conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Assessments of the Modulation Type with Regard to Intelligibility and Sound Quality

Development of Bone-Conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Assessments of the Modulation Type with Regard to Intelligibility and Sound Quality

Sound source localization in the horizontal plane through the bilaterally applied bone-conducted ultrasonic hearing aids

Bone-conducted ultrasound (BCU) can be perceived not only by normal hearing but also by the profoundly hearing impaired who cannot make use of a conventional hearing aid. BCU hearing aid (BCUHA), in which an ultrasonic carrier is amplitude-modulated (AM) by collected external sound and presented through a bone-conduction vibrator onto the mastoid portion, has been developed for the profoundly hearing impaired. To obtain useful information in order to realize accurate sound source localization through the BCUHAs. In this study, localization performance in the horizontal plane through bilaterally applied BCUHAs was investigated by psychological experiments. Results show that subjects hardly lateralized when the BCUHAs were simply applied bilaterally with the double-sideband modulation method. On the other hand, the localization performances were improved when the inter-lateral intensity and time differences of presenting signals of BCUHAs were enhanced on the basis of those of the collected external sounds and when the “transposed modulation” was employed as the modulation method. Our results suggest the necessity of the inter-lateral cooperative system to modify the spatial parameters of the output signal for accurate sound localization through the BCUHAs.

3Pb5-11 Development of a Bone-conducted Ultrasonic Hearing Aid (BCUHA) for the Profoundly Deaf : Evaluation of Sound Quality using Semantic Differential Method(Poster Session)

3Pb5-11 Development of a Bone-conducted Ultrasonic Hearing Aid (BCUHA) for the Profoundly Deaf : Evaluation of Sound Quality using Semantic Differential Method(Poster Session)

3Pa5-17 Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf : Development of a Downsized Digital Prototype(Poster Session)

3Pa5-17 Bone-conducted Ultrasonic Hearing Aid for the Profoundly Deaf : Development of a Downsized Digital Prototype(Poster Session)

The effect of visual information in speech signals by bone-conducted ultrasound

A prototype for a bone-conducted ultrasonic hearing aid was developed for the profoundly deaf. Previous studies using bone-conducted ultrasonic hearing aid revealed intelligibility only with the use of acoustic media in transmitting language information. In this study, we investigated the effects of visual information (lip-reading information) on intelligibility in bone-conducted ultrasound perception of normal-hearing individuals. We found that lip-reading information had clear effects on bone-conducted ultrasound perception, showing that simultaneous presentation of audio and visual information improved intelligibility to levels sufficient for speech perception. Our findings also suggested the efficacy of use of signal processing techniques in improving the intelligibility of prior consonants. NeuroReport 21:119–122

Comparison between bone-conducted ultrasound and audible sound in speech recognition

Conclusion: This study showed that it is possible to transmit language information using bone-conducted ultrasound (BCU) in normal-hearing subjects. Our results suggest the possibility of a difference in speech recognition between BCU and air-conducted audible sound (ACAS). Objective: Ultrasound was audible when delivered by bone conduction. Some profoundly deaf subjects as well as normal-hearing subjects can discriminate BCU whose amplitude is modulated by different speech sounds. These findings suggest the usefulness of developing a bone-conducted ultrasonic hearing aid (BCUHA). However, the characteristics of BCU are still poorly understood. The aim of the present study was to compare BCU and ACAS in terms of their associated speech perception tendency and to investigate the different perceptual characteristics of BCU and ACAS. Subjects and methods: Speech discrimination tests using both BCU and ACAS were performed with normal-hearing subjects. BCU and ACAS were compared for intelligibility and hearing confusion. Results: With BCU, the maximum percentage correct totaled about 75%. Our comparison of the hearing confusion with ACAS and BCU according to the individual syllabic nuclear group showed a clear difference in the incorrect rates. In addition, the stimulus nuclear groups were often perceived in other nuclear groups in BCU.

Assessment of ability to discriminate frequency of bone-conducted ultrasound by mismatch fields

According to previous studies, ultrasound can be perceived through bone conduction and ultrasound amplitude modulated by different speech sounds can be discriminated by some profoundly deaf subjects as well as the normal-hearing. These findings suggest the usefulness of development of a bone-conducted ultrasonic hearing aid (BCUHA) for profoundly deaf subjects. In this study, with a view to developing a frequency modulation system in a BCUHA, the capability to discriminate the frequency of sinusoidal bone-conducted ultrasound (BCU) was evaluated by measuring mismatch fields (MMF). We compared MMFs between BCU (standard stimuli were 30 kHz, and deviant stimuli were 27 and 33 kHz) and air-conducted audible sound (ACAS; standard stimuli were 1 kHz, and deviant stimuli were 900 and 1100 Hz). MMFs were observed in all subjects for ACAS, however, not observed in a few subjects for BCU. Further, the mean peak amplitudes of MMF for BCU were significantly less than those for ACAS. These findings indicate that the discrimination capability of frequency of sinusoidal BCU is inferior to that of ACAS. It was also demonstrated that normal hearing could to some extent discriminate differences in frequency in sinusoidal BCU. The results indicate a possibility of transmission system for language information making use of frequency discrimination.

Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Sensorineural Deaf

Development of a Bone-conducted Ultrasonic Hearing Aid for the Profoundly Sensorineural Deaf

RELATIONSHIP BETWEEN DETECTING PITCH VIA BONE-CONDUCTED ULTRASOUND AND EIGENFREQUENCIES OF HUMAN HEAD

This paper describes the relationship between the eigenfrequencies of CT scanned realistic human head model and the subjective detecting pitch, which is given by providing the bone-conducted ultrasound. Our goal is to develop the optimal bone-conducted ultrasonic hearing aid for profoundly hearing-impaired persons. An ascent of a speech intelligibility is the requirement of hearing aid. To improve it, the perception mechanism of the bone-conducted ultrasound must be clarified, but the conclusive agreement of it has not been reached yet, although many hypotheses were reported. The authors feel an interest in the detecting pitch of bone-conducted ultrasound with no frequency-dependence and predict that the cochleae are related to the perception mechanism for bone-conducted ultrasound, since it has been verified that the auditory cortex responds to bone-conducted ultrasound by MEG study. In this paper, waves propagating from the mastoid to both cochleae are numerically analyzed and the characteristics of transfer functions are estimated as a first step to clarifying the perception mechanism for detecting pitch of bone-conducted ultrasonic stimuli.

Development of bone-conducted ultrasonic hearing aid

Development of bone-conducted ultrasonic hearing aid