Perception of Bone-conducted Ultrasound Assessed by Optical Measurements of Tympanic Membrane Vibration

Abstract

To clarify mechanisms of the bone-conducted ultrasonic (BCU) perception, tympanic membrane (TM) vibrations under BCU stimuli were measured in a human subject using a laser Doppler vibrometer (LDV). We presented a signal processing algorithm to increase the SNRs (signal-to-noise ratios) of measured LDV signals by removing only optical noise components from the wave signals. Further, we analyzed the TM vibrations using the presented method to investigate the contribution of nonlinear distortion in the BCU perception, i. e. the possibility of generating the audible subharmonics. As a result, we did not find any audible signals corresponding to the subjective pitch of BCU in the TM vibrations. This suggests that there is no evidence for nonlinear distortion in the outer and middle ear.