Assessment of detection threshold and temporal resolution of distantly presented bone-conducted ultrasonic hearing

Abstract

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural hearing-impaired and has been applied to a novel hearing aid. The vibrator is usually pressed against a part of the cranial bone behind the ear (mastoid process); however, BCU presented to parts of the body distant from the head can be perceived. In this study, to assess the basic properties of distantly 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. Furthermore, temporal modulation transfer functions (TMTFs), which reflect the temporal resolution of hearing, were estimated for the distantly presented 30 kHz carrier. The results showed that BCU presented to parts of the body distant from the head, including the lower arm, can be perceived at least by normal-hearing persons, whereas the threshold increased depending on the distance from the head. Moreover, the temporal resolutions of the hearing of BCU distantly presented to the neck and the upper and lower arms were comparable to that distantly presented to the mastoid process of the temporal bone.