耳廓外(wai)側面有許多(duo)卷部，形同(tong)一(yi)組凹面鏡，它們可(ke)以(yi)是外(wai)界傳來的聲(sheng)(sheng)音發生反射和(he)折射，從而(er)使聲(sheng)(sheng)音在(zai)麥(mai)克(ke)風(feng)(feng)(feng)位置(zhi)處(chu)的聲(sheng)(sheng)壓增(zeng)大。與耳背式(shi)助(zhu)(zhu)聽(ting)器(qi)(qi)相比，耳內(nei)式(shi)助(zhu)(zhu)聽(ting)器(qi)(qi)的麥(mai)克(ke)風(feng)(feng)(feng)位于耳內(nei)，其助(zhu)(zhu)聽(ting)效果就是因(yin)為這一(yi)原理而(er)增(zeng)強。耳內(nei)式(shi)與耳背式(shi)助(zhu)(zhu)聽(ting)器(qi)(qi)所占耳甲腔/或(huo)外(wai)耳道(dao)外(wai)耳道(dao)的解(jie)剖外(wai)置(zhi)不(bu)(bu)同(tong)，且不(bu)(bu)同(tong)款式(shi)的耳內(nei)式(shi)助(zhu)(zhu)聽(ting)器(qi)(qi)的麥(mai)克(ke)風(feng)(feng)(feng)位置(zhi)不(bu)(bu)同(tong)，因(yin)此(ci)其聲(sheng)(sheng)增(zeng)益也有所不(bu)(bu)同(tong)。高建(jian)林的實驗(yan)說(shuo)明CIC麥(mai)克(ke)風(feng)(feng)(feng)處(chu)的聲(sheng)(sheng)增(zeng)益大，其次(ci)為ITC，再者ITE。