The microphone was making a strange whistling sound.

扩音器发出一种奇怪的哨音。

《牛津词典》

Obviously, you need a microphone and a sound card.

显然，你需要一个麦克风和一个声卡。

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But the microphone and chip in the device sample the incoming sound and produce an inverted wave that cancels out just the sound of the drill.

但是装置里的麦克风和芯片从传入的声音中采样，并且产生抵消牙钻声的反向波。

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Something that might make the next iPod even more useful would be the addition of a built-in microphone sound-in port for an external microphone to record sound.

FORBES: Magazine Article

Murray said that technical difficulties prevented the microphone from picking up sound, the drill steel was blocking the microphone, and a line broke.

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Beyond headphones, there's a line out for connecting it to a sound system, and a line in and microphone jack for adding external sound to the set.

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