JosephinaAlhambra
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Noise reduction headphones actively produce their own sound waves in order to cancel out external sound waves. A microphone in the headphones receives waves of one frequency. A loudspeaker in the headphones then produces a wave of that frequency but of a different phase. What is the phase difference between the external sound wave and the wave produced by the loudspeaker in the headphones? A. 90 B.180 C 270 D 360



Answer :

AL2006
If you want to use it to cancel out the external wave, then it has to be exactly the same frequency and exactly 180 degrees out of phase.

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