High-End Noise Cancelling Headphones
As surrounding noise is captured by the microphone, the electronic circuitry generates a signal of the opposite phase, that is to say, peaks and valleys are reversed.
The sound with the reversed phase is emitted by the driver and cancels out the noise as it enters the ear.
Noise is kept low at the ear, making it possible to enjoy music without raising the volume unnecessarily.
These headphones are designed to attenuate low frequency inconsonant noise of 1,500 Hz or less. They do not have great effect on relatively high frequency components such as automobile horns, telephone rings or the human voice.