抄録
イヤホンやヘッドホンシステムでの受聴時にホールやライブ会場といった特定の場所での音環境を立体的に再現することは容易ではない.そこで注目されているのが,立体音響方式である.立体音響とは音を録音再生する際に三次元的な音の方向や距離,拡がりなどを再生する方式のことである.立体音響の方式の一つにヒトの頭,耳介,外耳道などによる周波数特性の変化を補償する音源の音像定位を再現するものがある.本報告では,音響管(245mm)による2マイクロホン法(4個のマイクロホン使用mic1,mic2,mic3,mic4)に基づいて,外耳道の音圧反射係数と音響インピーダンスを算出した.その結果から,被験者(9名)の外耳道音圧反射係数が0.2前後の最小値を示す周波数は2kHzと8kHz付近であること,外耳道の音響インピーダンスのピークは200Hz〜1kHzと6kHz〜9kHz付近にあることがわかり,大きな個人差が観測された.
Computer simulation of acoustic scenes is an important prerequisite of rendering. Technology for 3-D sound reproduction, the so-called "audio front end" or the "acoustic human-machine interface" is an essential component of VR systems, which must be capable of fulfilling high quality standards involving psycho-acoustically relevant cues. One of the factors that can affect the sound transmission in the ear is the acoustic impedance of the ear canal. Its importance is related to the contribution of other elements involved in the transmission such as the earphone impedance. In order to determine the acoustic impedances used for human ear canals, the standardized method for measurement of complex impedances used for the measurement of the audiometric earphone impedances was applied. It is based on the transfer function between two microphone locations in an impedance tube. The end of the tube representing the measurement plane was placed at the ear canal entrance. Thus, the impedance seen from the entrance inward was measured on 9 subjects. From the results, (a) the dips (about 0.2) of the sound pressure reflectances of the ear canal are in about 2kHz and 8kHz, and (b) the peaks of the ear canal impedances are in about 200Hz to 1kHz and 6kHz to 9kHz.
