Study on the acoustic reflex in binaural hearing by means of the impedance method (author's transl)

Abstract

The human acoustic reflex in binaural and monaural hearing were observed in free field by means of the impedance method to clarify the mechanisms of the intratympanic muscles.The results were obtained as follows.1) When the sound source was the front, the impedance-change was larger in binaural hearing than in monaural hearing. (Phenomenon I )2) When the sound source was the side, the difference of the impedance-change between both ear was smaller in binaural hearing than in monaural hearing, furthermore the impedancechange was larger of ipsilateral ear of the sound source than of contralateral one everytime. (Phenomenon II)3) It was deduced that both Phenomenon I and II obtained from this study were caused by that the binaural interaction generated in superior olivary complex had influence on the acoustic reflex with bilateral are.4) The meaning of Phenomenon I was that the binaural summation as result of binaural interaction was confirmed by observation on the acoustic reflex.The meaning of Phenomenon II was that the intratympanic muscles which contracted as reflection of binaural interaction was able to transmit loud sound changing for attenuated one to each inner ear keeping the approximate value of sound pressure-difference between both ear.In conclusion, it was suggested that the acoustic reflex not only protect inner ear from loud sound but also perticipate in the mechanisms of the directional hearing.