Development of a novel hearing-aid for the profoundly deaf using bone-conducted ultrasonic perception: Evaluation of transposed modulation

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 articulation and sound quality. BCU speech is accompanied by a strong high-pitched tone and contain some distortion. In this study, transposed modulation, that can be expected to reduce the high-pitched tone was newly employed as a modulation method in the BCUHA, and its resulting articulation, intelligibility and sound quality were evaluated. The results showed that transposed modulation showed nearly equal articulation and intelligibility scores to and better sound quality than the existing method, DSB-TC modulation. These results provide useful information for further development of the BCUHA.