聽覚の研究（外耳道）（2）

（3）外耳道の音響特性

　a）Meyer E.：Handbuch der Physik. Bd. 8，Akustik

外耳道はそれを通つて内方に音響の伝導が起るのであるが，一端開口せる共鳴器を思わせるその壁面殊に鼓膜によつて閉鎖された管端は強固ではないから減衰が比較的大であろう．外耳道は音波に較べて短いからその固有振動は高く約2800Hzで．あろう，Rinneはこれf⁴（2733）を，Helmholtzはf⁴及びC4（2048）を，Hansenはd⁴（2298）及びa⁴（3444）を与えている．

　b）Bekesy G. V.：Annalen der Physik, Bd. 14, S. 51. 1932

　ONCHI referring to works of Bekesy, Wiener, and Onchi in the role of external ear canal as organ of resonance with their calculated and attained figure of value of that function along with theoretically derived ones of Meyer, Rinne, Helmholtz, and Hansen as further references says the frequency of free vibration of the external auditory canal is 2000 to 3000 c.p.s.. Furthermore, that by pointing out the fact that the sound by striking against the head and tympanic memdrane is further reenforced by its diffraction which adds to the 20 DB the value for increment of sound pressnure by external canal resonance action, the total of which the author considers an intergral part of the system of hearing.