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| Sony Noise Canceling Headphones |
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Noise Cancellation: Passive VS. Active By CNet
The low-tech, or passive, way to cancel noise is simply to wear closed-back, circumaural (around the ear) headphones or very snug earbuds. These shield your ears by sealing them off from the outside world. Active noise cancellation, on the other hand, is far more complicated and involves some serious science.
First, tiny microphones, one on each earpiece, detect ambient noise before it gets to your ears. Then the noise-cancellation circuitry, usually housed in an external module, essentially inverts the captured signal, turning the noise's sound wave upside down. Before you know it, the noise-cancellation system adds the sonic opposite of the external noise to whatever you're listening to, thereby eliminating most of the pollution and leaving you with just your music. |
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