耳廓外(wai)側面(mian)有許多卷部,形同一組凹面(mian)鏡,它們可以是(shi)外(wai)界傳(chuan)來的(de)(de)聲(sheng)(sheng)音發生反(fan)射和折射,從而使聲(sheng)(sheng)音在麥克風位置處(chu)(chu)的(de)(de)聲(sheng)(sheng)壓增(zeng)(zeng)大。與耳背式(shi)(shi)(shi)助(zhu)聽器相比,耳內(nei)式(shi)(shi)(shi)助(zhu)聽器的(de)(de)麥克風位于耳內(nei),其(qi)助(zhu)聽效果就是(shi)因(yin)為(wei)(wei)這(zhe)一原理(li)而增(zeng)(zeng)強。耳內(nei)式(shi)(shi)(shi)與耳背式(shi)(shi)(shi)助(zhu)聽器所占耳甲腔/或外(wai)耳道(dao)(dao)外(wai)耳道(dao)(dao)的(de)(de)解剖外(wai)置不(bu)同,且不(bu)同款(kuan)式(shi)(shi)(shi)的(de)(de)耳內(nei)式(shi)(shi)(shi)助(zhu)聽器的(de)(de)麥克風位置不(bu)同,因(yin)此其(qi)聲(sheng)(sheng)增(zeng)(zeng)益也有所不(bu)同。高建林的(de)(de)實驗說(shuo)明CIC麥克風處(chu)(chu)的(de)(de)聲(sheng)(sheng)增(zeng)(zeng)益大,其(qi)次為(wei)(wei)ITC,再者ITE。