耳廓外(wai)(wai)側(ce)面有許多(duo)卷部，形同(tong)一組凹面鏡，它們可以(yi)是外(wai)(wai)界傳來(lai)的聲(sheng)音發生反射和折射，從而使聲(sheng)音在麥(mai)(mai)克(ke)(ke)風(feng)位(wei)(wei)置(zhi)處(chu)的聲(sheng)壓增(zeng)大(da)。與(yu)耳背式(shi)助(zhu)(zhu)聽(ting)器(qi)相比，耳內(nei)式(shi)助(zhu)(zhu)聽(ting)器(qi)的麥(mai)(mai)克(ke)(ke)風(feng)位(wei)(wei)于耳內(nei)，其助(zhu)(zhu)聽(ting)效果就(jiu)是因(yin)為(wei)這一原理而增(zeng)強。耳內(nei)式(shi)與(yu)耳背式(shi)助(zhu)(zhu)聽(ting)器(qi)所占耳甲腔(qiang)/或外(wai)(wai)耳道(dao)外(wai)(wai)耳道(dao)的解(jie)剖外(wai)(wai)置(zhi)不(bu)同(tong)，且不(bu)同(tong)款式(shi)的耳內(nei)式(shi)助(zhu)(zhu)聽(ting)器(qi)的麥(mai)(mai)克(ke)(ke)風(feng)位(wei)(wei)置(zhi)不(bu)同(tong)，因(yin)此其聲(sheng)增(zeng)益也有所不(bu)同(tong)。高建林的實驗說明CIC麥(mai)(mai)克(ke)(ke)風(feng)處(chu)的聲(sheng)增(zeng)益大(da)，其次為(wei)ITC，再者ITE。