開放と密閉条件下における外耳道内の2マイクロホン法による音響特性計測

摘要

バイノーラル技術は鼓膜位置の音を録音，合成，再生する方法の1つとして重要である．鼓膜のインピーダンスは開放状態において外耳での反響に大きく影響を及ぼし，外耳道にイヤホンを挿入して音を聴くときに重要である．本報告では，鼓膜のインピーダンスを2マイクロホン法により以下の条件下で測定した．（a）外耳道が開放状態のときにスピーカからの音と骨導音により駆動した場合，（b）耳が塞がれた状態でイヤホン（ER-6）からの音と骨導音により駆動した場合．鼓膜のインピーダンス値（MKSΩ）は，各個人の外耳道を直径7．2mmから8．3mmで一定の音響管とみなして計算した．結果から，個人間で外耳道の形状，鼓膜のインピーダンスに変動性があることがわかった．%The binaural technique is used for methods of sound recording, synthesis and reproduction, where the signals in focus are the acoustic signals at the eardrums. The impedance presented to the ear canal by the eardrum strongly affects the free-field response of the ear in the vicinity of resonance and is crucial when the ear is driven by an earphone inserted into the canal. In this paper, the parameter values of the eardrum impedance were measured by the two-microphone systems proposed with the following conditions: (a) the free-field response when the ear is driven by a loudspeaker and a bone conduction (b) the oclluded-ear response when the ear is driven by an earphone (ER-6) and a bone conduction. The eardrum impedance values (MKSΩ) were calculated values based on the simplifying assumptions that the human ear canal can be treated as a uniform cylinder with diameters from 7.2mm to 8.3mm. From the results, it can be found that the variability of ear-canal geometry and ear impedance among individuals.