Sound transmission by cartilage conduction in ear with fibrotic aural atresia.

A hearing aid using cartilage conduction (CC) has been proposed as an alternative to bone conduction (BC) hearing aids. The transducer developed for this application is lightweight, requires a much smaller fixation force than a BC hearing aid, and is more convenient to use. CC can be of great benefit to patients with fibrotic aural atresia. Fibrotic tissue connected to the ossicles provides an additional pathway (termed fibrotic tissue pathway) for sound to reach the cochlea by means of CC. To address the function of fibrotic tissue pathway, BC and CC thresholds were measured in six ears with fibrotic aural atresia. The relationship between the CC thresholds and the results of computed tomography was investigated. In the ears with the presence of a fibrotic tissue pathway, the CC thresholds were lower than the BC thresholds at 0.5 and 1.0 kHz. At 2.0 kHz, no significant difference was observed between the BC and CC thresholds. The current findings suggest that sound in the low to middle frequency range is transmitted more efficiently by CC via a fibrotic tissue pathway than BC. The development of hearing devices using CC can contribute to rehabilitation, particularly in patients with fibrotic aural atresia.

Human ultrasonic hearing is induced by a direct ultrasonic stimulation of the cochlea.

Ultrasound can be perceived by bone-conduction. The cochlear basal turn is involved in processing bone-conducted ultrasound (BCU) information. Previous studies have suggested that ultrasonic perception is induced by ultrasound itself. In contrast, it has also been suggested that a lower frequency sound is generated in non-linear process during the transmission pathway to the cochlea to induce an auditory sensations. To address this issue, we assessed cisplatin-induced changes in BCU sensitivity at 27, 30 and 33kHz in 20 participants (40 ears) who were scheduled to undergo cisplatin chemoradiation therapy. Following the treatment, 62.5% ears were diagnosed with hearing loss according to the criteria of the American Speech-Language-Hearing Association. As expected, significant increases in sensitivity threshold were observed for air-conducted sounds ranging from 8 to 14kHz. In contrast, the BCU threshold significantly decreased after the treatment. Considering that both air-conducted high-frequency sound and BCU are perceived in the cochlear basal turn, these findings indicate that ultrasonic perception is independent of hearing a lower frequency sound generated in non-linear process. In addition, our findings support the hypothesis that ultrasound itself induces ultrasonic perception in the cochlea. The observed cisplatin-induced increase in BCU sensitivity may be explained by hypersensitivity associated with outer hair cells' disorder.

Hearing aids reduce overestimation in pre-fitting self-assessment.

OBJECTIVE: When asking about hearing disability, the self-reported answers are not always equivalent to those of their family and neighbors. It is often experienced that family and neighbors indicate more severe hearing disability. Hearing difficulty itself may prevent hearing impaired subjects from understanding the degree of their own hearing disability. If their hearing impairment interferes with self-assessment of unaided hearing ability, it may change after a non-hearing aid user begins using hearing aids. METHODS: Thirty-four adults who had almost no experience with using hearing aids participated in this study. Unaided hearing disability was assessed with visual analog scale (VAS) and ten 5-point category scales. The assessment was performed not only by the subject (pre-fitting self-assessment) but also by his/her family members, presumed to be understanding persons regarding the degree of his/her hearing disability (family-assessment). For evaluating the effect of amplification on self-assessment, re-assessment was performed more than three months later (post-fitting self-assessment). The overestimation in the pre-fitting self-assessment and the effect of amplification were investigated in comparison to the family- and post-fitting self-assessments. RESULTS: The pre-fitting self-, family- and post-fitting self-VAS values for total hearing abilities were 50.5±15.6, 45.1±14.7 and 34.3±18.8, respectively. The pre-fitting self-VAS value was significantly higher than the family- and post-fitting self-VAS values (p<0.05 and p<0.01, respectively). For the 5-point category scale, the pre-fitting self-assessment was better than the family- and post-fitting self-assessments. Significant differences were observed in 1 and 2 situations, as compared with the family- and post-fitting self-assessments, respectively. These findings suggest the involvement of overestimation in pre-fitting self-assessment and its reduction after amplification with hearing aids. Although the pre-fitting self- and the family-VAS values were independent of the results of audiometric tests, the post-fitting self-VAS value was significantly related to the pure tone threshold and maximum speech recognition score (p<0.05). Regarding the changes in self-VAS values after amplification, the higher the pre-fitting self-VAS value, the larger the decrease in the self-VAS value. Thus, amplification with hearing aids may reduce overestimation and change self-assessment to reflect the audiometric assessments. CONCLUSION: The pre-fitting self-assessment of hearing disability involves over estimation which is exacerbated by hearing difficulty. A high pre-fitting VAS value may reflect a large overestimation in hearing ability. This overestimation can be improved by the amplification with hearing aids.

Peripheral perception mechanism of ultrasonic hearing.

Ultrasound can be perceived by bone conduction, and its characteristics differ from those of air-conducted audible sound (ACAS) in some respects. Despite many studies on ultrasonic hearing, the details have not yet been clarified. In this study, to elucidate the perception mechanism, the masking of bone-conducted ultrasound (BCU) produced by ACAS and the sensitivity of BCU in hearing impaired subjects were evaluated. We found that BCU was masked by high frequency ACAS, especially in the frequency range of 10-14 kHz. The most effective masker frequency depended on masker intensity. For hearing impaired subjects, the pure tone thresholds at 1-8 kHz and the maximum audible frequencies at cut-off intensities of 70-100 dB HL were significantly associated with the BCU threshold (p < 0.01 or p < 0.05). No subjects with estimated total loss of the inner hair cell system in the cochlear basal turn could hear BCU. These results suggest the peripheral perceptual region to be located in the cochlea. The results of masking show the faster excitation spread to the lower frequency range, depending on the intensity. This faster excitation spread may be due to nonlinearity in cochlear mechanics, which may work even without cochlear amplifier, and induce unique characteristics of BCU.