Cartilage Conduction Is Characterized by Vibrations of the Cartilaginous Portion of the Ear Canal

PLoS One

Tadashi Nishimura¹  Tadashi Kitahara¹  Toshiaki Yamanaka¹  Osamu Saito¹  Ryosuke Miyamae¹  Ryota Shimokura¹  Hiroshi Hosoi²  Harry Levitt³ 

[1] Department of Otolaryngology-Head and Neck surgery, Nara Medical University, Kashihara, Japan;Nara Medical University, Kashihara, Japan;The City University of New York, New York, New York, United States of America

关键词: Cartilage;    Ears;    Vibration;    Skull;    Cochlea;    Hearing disorders;    Mastoid process;    Sound pressure;   

DOI  :  10.1371/journal.pone.0120135

学科分类：医学（综合）

来源: Public Library of Science

【 摘 要 】

Cartilage conduction (CC) is a new form of sound transmission which is induced by a transducer being placed on the aural cartilage. Although the conventional forms of sound transmission to the cochlea are classified into air or bone conduction (AC or BC), previous study demonstrates that CC is not classified into AC or BC (Laryngoscope 124: 1214–1219). Next interesting issue is whether CC is a hybrid of AC and BC. Seven volunteers with normal hearing participated in this experiment. The threshold-shifts by water injection in the ear canal were measured. AC, BC, and CC thresholds at 0.5–4 kHz were measured in the 0%-, 40%-, and 80%-water injection conditions. In addition, CC thresholds were also measured for the 20%-, 60%-, 100%-, and overflowing-water injection conditions. The contributions of the vibrations of the cartilaginous portion were evaluated by the threshold-shifts. For AC and BC, the threshold-shifts by the water injection were 22.6–53.3 dB and within 14.9 dB at the frequency of 0.5–4 kHz, respectively. For CC, when the water was filled within the bony portion, the thresholds were elevated to the same degree as AC. When the water was additionally injected to reach the cartilaginous portion, the thresholds at 0.5 and 1 kHz dramatically decreased by 27.4 and 27.5 dB, respectively. In addition, despite blocking AC by the injected water, the CC thresholds in force level were remarkably lower than those for BC. The vibration of the cartilaginous portion contributes to the sound transmission, particularly in the low frequency range. Although the airborne sound is radiated into the ear canal in both BC and CC, the mechanism underlying its generation is different between them. CC generates airborne sound in the canal more efficiently than BC. The current findings suggest that CC is not a hybrid of AC and BC.

【 授权许可】

CC BY