耳廓外(wai)(wai)側面有(you)許多卷(juan)部，形同(tong)一組凹面鏡，它們可以是(shi)(shi)外(wai)(wai)界傳(chuan)來的聲(sheng)(sheng)音發(fa)生反射和(he)折射，從(cong)而使聲(sheng)(sheng)音在麥(mai)克(ke)風位(wei)置(zhi)處(chu)的聲(sheng)(sheng)壓(ya)增(zeng)(zeng)大。與(yu)(yu)耳背(bei)式(shi)助(zhu)聽器(qi)相比，耳內(nei)式(shi)助(zhu)聽器(qi)的麥(mai)克(ke)風位(wei)于耳內(nei)，其助(zhu)聽效果就(jiu)是(shi)(shi)因為這一原理而增(zeng)(zeng)強(qiang)。耳內(nei)式(shi)與(yu)(yu)耳背(bei)式(shi)助(zhu)聽器(qi)所(suo)占耳甲(jia)腔(qiang)/或外(wai)(wai)耳道外(wai)(wai)耳道的解剖外(wai)(wai)置(zhi)不同(tong)，且不同(tong)款式(shi)的耳內(nei)式(shi)助(zhu)聽器(qi)的麥(mai)克(ke)風位(wei)置(zhi)不同(tong)，因此其聲(sheng)(sheng)增(zeng)(zeng)益也有(you)所(suo)不同(tong)。高建林(lin)的實驗說明CIC麥(mai)克(ke)風處(chu)的聲(sheng)(sheng)增(zeng)(zeng)益大，其次為ITC，再者ITE。