Pitch estimation of bone‐conducted ultrasound

Abstract

Although ultrasound is perceptible through bone conduction, its perception mechanism has been clarified only slightly. The subjective pitch of bone‐conducted ultrasound (BCU) sounds like a tone or harmonic sound of ten‐odd kilohertz, independent of its own frequency. It has been difficult to determine the frequency of the pitch precisely because the pitch varies among listeners and with the position and strength of BCU stimulation, moreover; BCU hearing is not masked well by air‐conducted (AC) band‐pass noise. In this study, the BCU pitch‐perception mechanism was investigated using beats with AC tones. The AC tones of 10–17 kHz, for which the presence of the pitch of BCU had been expected, were presented sequentially together with BCU (30 kHz) stimulation. Listeners were asked whether or not they were able to hear beats. For comparison, bone‐conducted (BC) harmonic sounds of audible frequency components (e.g., 11–16 kHz, 1‐kHz step) were also investigated. Results showed that no beat was heard between the AC tones and the BCU, whereas beats between the AC tones and the BC harmonic sounds were heard, suggesting the possibility that the pitch‐perception mechanism of BCU is different from those of AC and BC sounds in this audible frequency area.