耳(er)廓外(wai)側面有許多卷部，形(xing)同(tong)(tong)(tong)一組凹(ao)面鏡，它們可以(yi)是外(wai)界傳來(lai)的(de)(de)聲(sheng)音發生反射和折射，從而使(shi)聲(sheng)音在麥克(ke)風位(wei)置(zhi)處(chu)的(de)(de)聲(sheng)壓增(zeng)大。與(yu)耳(er)背(bei)(bei)式(shi)助聽(ting)(ting)(ting)器相比，耳(er)內(nei)(nei)式(shi)助聽(ting)(ting)(ting)器的(de)(de)麥克(ke)風位(wei)于耳(er)內(nei)(nei)，其(qi)助聽(ting)(ting)(ting)效果就(jiu)是因為這(zhe)一原理而增(zeng)強(qiang)。耳(er)內(nei)(nei)式(shi)與(yu)耳(er)背(bei)(bei)式(shi)助聽(ting)(ting)(ting)器所占耳(er)甲(jia)腔/或外(wai)耳(er)道(dao)外(wai)耳(er)道(dao)的(de)(de)解剖(pou)外(wai)置(zhi)不(bu)同(tong)(tong)(tong)，且不(bu)同(tong)(tong)(tong)款式(shi)的(de)(de)耳(er)內(nei)(nei)式(shi)助聽(ting)(ting)(ting)器的(de)(de)麥克(ke)風位(wei)置(zhi)不(bu)同(tong)(tong)(tong)，因此(ci)其(qi)聲(sheng)增(zeng)益(yi)也有所不(bu)同(tong)(tong)(tong)。高建林的(de)(de)實驗說明CIC麥克(ke)風處(chu)的(de)(de)聲(sheng)增(zeng)益(yi)大，其(qi)次為ITC，再者ITE。