Nishimura Tadashi, Hosoi Hiroshi, Saito Osamu, Akasaka Sakie, Shimokura Ryota, Yamanaka Toshiaki, Kitahara Tadashi
Department of Otolaryngology-Head and Neck Surgery, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan.
President's Office, Nara Medical University, Kashihara, Nara 634-8522, Japan.
J Acoust Soc Am. 2020 Aug;148(2):469. doi: 10.1121/10.0001671.
When a transducer is placed on aural cartilage, relatively loud sound becomes audible in a conduction form termed cartilage conduction (CC). Previous studies have revealed the acoustical differences between CC and conventional air or bone conduction. This study elucidates the working principle of CC through measurements of threshold shifts by water injection into the ear canal under various fixation place conditions. Seven volunteers with normal hearing participated. A lightweight transducer was fixed for three CC conductions (on the tragus, antitragus, and intertragal incisure), and two non-CC conditions (on the pre-tragus and mastoid). Thresholds were measured at 500, 1000, and 2000 Hz in the 0%-, 40%-, and 80%-water injection conditions. Results for the three CC conditions revealed unique features different from those for the non-CC conditions. For the CC conditions, the thresholds increased by the 40%-water injection at all frequencies. However, with additional water injection (80%-water injection), the thresholds decreased at 500 and 1000 Hz; in particular, dramatically at 500 Hz. The results suggest that a direct vibration of the aural cartilage is important to obtaining the significant contribution of airborne sound to hearing above 1000 Hz. Fixation place results in no significant difference in acoustic features among CC conditions.
当换能器置于耳廓软骨上时，相对较大的声音会以一种称为软骨传导（CC）的传导形式被听到。先前的研究已经揭示了CC与传统空气传导或骨传导之间的声学差异。本研究通过在各种固定位置条件下向耳道内注水来测量阈值变化，从而阐明CC的工作原理。七名听力正常的志愿者参与了研究。一个轻质换能器被固定用于三种CC传导情况（在耳屏、对耳屏和耳屏间切迹上），以及两种非CC情况（在耳屏前和乳突上）。在0%、40%和80%注水条件下，分别在500、1000和2000赫兹测量阈值。三种CC情况的结果显示出与非CC情况不同的独特特征。对于CC情况，在所有频率下，40%注水时阈值升高。然而，随着进一步注水（80%注水），500和1000赫兹时阈值降低；特别是在500赫兹时显著降低。结果表明，耳廓软骨的直接振动对于在1000赫兹以上获得空气传播声音对听力的显著贡献很重要。固定位置在CC情况之间的声学特征上没有显著差异。
