Suppression of distortion product otoacoustic emissions induced by bone-conducted ultrasonic stimulation

Abstract Psychoacoustic studies have demonstrated that ultrasonic stimulation via bone conduction evokes auditory sensations, suggesting involvement of cochlear processing. To complement these behavior-based findings, this study objectively investigates how bone-conducted ultrasound (BCU) influences cochlear processes contributing to distortion product otoacoustic emissions (DPOAEs) by quantifying changes in DPOAEs. If BCU influences the cochlear region at which a DPOAE is measured, the DPOAE is expected to decrease (suppression). Three key questions were addressed: (1) which cochlear frequency region is affected by BCU; (2) whether the suppression is ultrasonic-frequency dependent; (3) whether different ultrasonic frequencies activate different regions. DPOAEs were measured across 3–14 kHz while an ultrasonic masker (26–42 kHz) was applied at different levels. We found that a sufficiently intense BCU is required to affect DPOAEs; in our results, +14 dB sensation level induced clear suppression at high frequencies (≈9–14 kHz), indicating that BCU mainly influences cochlear processes in the basal high-frequency region.