耳廓外(wai)(wai)側面(mian)有許多(duo)卷部，形同(tong)(tong)一組凹面(mian)鏡，它們可以是外(wai)(wai)界傳來的(de)聲(sheng)(sheng)音發生反(fan)射和(he)折射，從而(er)使聲(sheng)(sheng)音在麥(mai)克(ke)風位(wei)置處(chu)的(de)聲(sheng)(sheng)壓增(zeng)大(da)。與耳背(bei)式(shi)助聽(ting)(ting)器相比，耳內(nei)式(shi)助聽(ting)(ting)器的(de)麥(mai)克(ke)風位(wei)于耳內(nei)，其(qi)助聽(ting)(ting)效果(guo)就是因為這一原理而(er)增(zeng)強。耳內(nei)式(shi)與耳背(bei)式(shi)助聽(ting)(ting)器所占耳甲腔/或外(wai)(wai)耳道外(wai)(wai)耳道的(de)解(jie)剖(pou)外(wai)(wai)置不(bu)同(tong)(tong)，且不(bu)同(tong)(tong)款式(shi)的(de)耳內(nei)式(shi)助聽(ting)(ting)器的(de)麥(mai)克(ke)風位(wei)置不(bu)同(tong)(tong)，因此(ci)其(qi)聲(sheng)(sheng)增(zeng)益也有所不(bu)同(tong)(tong)。高建林的(de)實驗(yan)說明CIC麥(mai)克(ke)風處(chu)的(de)聲(sheng)(sheng)增(zeng)益大(da)，其(qi)次為ITC，再者ITE。