声学。测听设备校准用参照区。第1部分：纯音和耳挂式耳机的参考等效阈声压级。
Acoustics - Reference zero for the calibration of audiometric equipment - Part 1 : reference equivalent threshold sound pressure levels for pure tones and supra-aural earphones.
PC 121是一款挂耳式单耳通讯耳机，是廉价互联网电话和笔记本的理想选择。
The PC 121 is an over the ear monaural headset, ideal for inexpensive Internet telephony and laptop use.
PC 121是一款挂耳式单耳通讯耳机，是廉价互联网电话和笔记本的理想选择。
The PC 121 is an over the ear monaural headset, ideal for inexpensive Internet telephony and laptop use.
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