Identification of routes contributing to bone conduction hearing by means of measurement of vibrations of ossicular chain and cochlea in living humans

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K04021
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 20010:Mechanics and mechatronics-related
• Research Institution: Tottori University
• Principal Investigator: ARII Shiro 鳥取大学, 工学研究科, 准教授 (80222751)
• Co-Investigator(Kenkyū-buntansha): 片岡 英幸 鳥取大学, 医学部, 教授 (00224436) ; 長谷川 賢作 日本医科大学, 医学部, 教授 (60252847) ; 矢間 敬章 鳥取大学, 医学部, 助教 (30444631)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: 骨導聴力 / 伝音経路 / 耳小骨振動 / 生体計測 / シミュレーション

Outline of Final Research Achievements

Humans can perceive sound when the bones of the skull are excited by a vibrator. This phenomenon is normally referred to as hearing by bone conduction. Three bone conduction routes are proposed. (1) Sound radiated into the external ear canal is transmitted via the eardrum and the ossicular chain. (2) Vibrations of the bones are transmitted directly to the ossicular chain. (3) Vibrations of the bones are transmitted directly to the cochlea. In order to identify the routes contributing to bone conduction hearing, the tragus was excited by a vibrator and the vibrations of ossicular chain, cochlea, and external ear canal wall were measured in three living volunteers. Furthermore, the sound radiated into the external ear canal was measured in nine living volunteers. The exciting force was transmitted directly to the ossicular chain and the cochlea. However, the sound pressure radiated into the external ear canal was very low. The sound dose not contribute to the bone conduction route.

Free Research Field

機械力学・制御

Academic Significance and Societal Importance of the Research Achievements

ヒトの骨導聴力は，頭骨の振動が３通りの経路で伝達される聴力と言われている．(1)外耳道壁を介して外耳道内の空気および鼓膜を振動させて気導と同様に伝わる，(2)耳小骨に伝わり, その振動が蝸牛に伝わる，(3)直接蝸牛に伝わる，である．しかしながら，ヒトの生体においては十分に解明されていなかった．本研究では，ヒト生体での骨導加振時の耳小骨，外耳道後壁，蝸牛骨包の振動，および外耳道内音圧を計測し，これらの経路の検証を行なった．その結果，ヒトの骨導聴力の経路は，外耳道内の空気の振動による経路はなく，耳小骨の振動が蝸牛に伝播する経路，蝸牛に直接振動が伝播する経路の二つと考えられることが明らかとなった．