Peripheral perception mechanism of ultrasonic hearing.
Ultrasound can be perceived by bone conduction, and its characteristics differ from those of air-conducted audible sound (ACAS) in some respects. Despite many studies on ultrasonic hearing, the details have not yet been clarified. In this study, to elucidate the perception mechanism, the masking of bone-conducted ultrasound (BCU) produced by ACAS and the sensitivity of BCU in hearing impaired subjects were evaluated. We found that BCU was masked by high frequency ACAS, especially in the frequency range of 10-14 kHz. The most effective masker frequency depended on masker intensity. For hearing impaired subjects, the pure tone thresholds at 1-8 kHz and the maximum audible frequencies at cut-off intensities of 70-100 dB HL were significantly associated with the BCU threshold (p < 0.01 or p < 0.05). No subjects with estimated total loss of the inner hair cell system in the cochlear basal turn could hear BCU. These results suggest the peripheral perceptual region to be located in the cochlea. The results of masking show the faster excitation spread to the lower frequency range, depending on the intensity. This faster excitation spread may be due to nonlinearity in cochlear mechanics, which may work even without cochlear amplifier, and induce unique characteristics of BCU.
Department of Otolaryngology and Head & Neck surgery, Nara Medical University, 840 shijo-cho Kashihara, Nara 634-8522, Japan. t-nishim@naramed-u.ac.jp
Tadashi
T
Nishimura
Tadao
T
Okayasu
Yuka
Y
Uratani
Fumi
F
Fukuda
Osamu
O
Saito
Hiroshi
H
Hosoi
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D001306:Auditory Pathways / Q000503:physiopathology*; D001307:Auditory Perception; D001309:Auditory Threshold; D001844:Bone Conduction; D003051:Cochlea / Q000503:physiopathology*; D005260:Female; D006319:Hearing Loss, Sensorineural / Q000503:physiopathology* / Q000523:psychology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010470:Perceptual Masking; D013997:Time Factors; D014465:Ultrasonics; D014732:Vibration; D055815:Young Adult