Developments of novel vibrators using adhesive-tape and suction-cup for bone-conducted ultrasound presented to the chest, back, and upper limbs

Ultrasounds, high-frequency sounds above 20 kHz can be clearly heard by bone-conduction. This “bone-conducted ultrasound” (BCU) can be clearly heard even when presented to distal body parts from the head, such as the chest, back, and upper limbs. Previous studies have suggested that “distantly presented BCU” is expected to be applied to novel audio devices that can selectively transmit sound information to a specific user who touches the vibrator, without any sound leakage. In previous studies of the distantly presented BCU, vibrators were presented against the body (e.g., the chest or back) using an elastic band. However, this method is too complex and impractical. Therefore, improvement of the fixation method is crucial for the practical application of distantly presented BCU devices. In this study, we developed novel vibrators using adhesive tape and suction cups that are easier to fix than conventional method. Additionally, we investigated the effects of presentation site and contact area on the hearing threshold of distantly presented BCU. The results showed that BCU was perceptible at all sites where these vibrators could be fixed and that optimizing the contact area can improve BCU perception. These findings provide valuable insights for the development of practical vibrator fixation methods.