42 骨傳導閾值的起始遮蔽值Initial masking level = AC nontest ear + OE + 10 dB,其中OE指的是阻塞效應( occlusion effect),OE值在 1000 Hz之建議值為?
(A)supra-aural earphones:10 dB;insert earphones:0 dB
(B)supra-aural earphones:15 dB;insert earphones:5 dB
(C)supra-aural earphones:20 dB;insert earphones:10 dB
(D)supra-aural earphones:25 dB;insert earphones:20 dB