耳(er)(er)廓外(wai)(wai)側面(mian)有許多卷部，形同(tong)(tong)(tong)一(yi)組凹面(mian)鏡，它們可以是外(wai)(wai)界傳來的(de)(de)聲(sheng)音發生反射和折(zhe)射，從而使聲(sheng)音在麥(mai)克(ke)風(feng)位置處的(de)(de)聲(sheng)壓增(zeng)大。與耳(er)(er)背式(shi)(shi)(shi)助(zhu)聽器相比(bi)，耳(er)(er)內(nei)式(shi)(shi)(shi)助(zhu)聽器的(de)(de)麥(mai)克(ke)風(feng)位于耳(er)(er)內(nei)，其(qi)助(zhu)聽效果就是因為(wei)這一(yi)原(yuan)理而增(zeng)強。耳(er)(er)內(nei)式(shi)(shi)(shi)與耳(er)(er)背式(shi)(shi)(shi)助(zhu)聽器所(suo)占耳(er)(er)甲腔/或外(wai)(wai)耳(er)(er)道外(wai)(wai)耳(er)(er)道的(de)(de)解(jie)剖外(wai)(wai)置不(bu)同(tong)(tong)(tong)，且不(bu)同(tong)(tong)(tong)款式(shi)(shi)(shi)的(de)(de)耳(er)(er)內(nei)式(shi)(shi)(shi)助(zhu)聽器的(de)(de)麥(mai)克(ke)風(feng)位置不(bu)同(tong)(tong)(tong)，因此其(qi)聲(sheng)增(zeng)益也(ye)有所(suo)不(bu)同(tong)(tong)(tong)。高建林的(de)(de)實驗說明CIC麥(mai)克(ke)風(feng)處的(de)(de)聲(sheng)增(zeng)益大，其(qi)次(ci)為(wei)ITC，再者ITE。