Noise-cancelling headphones reduce unwanted ambient sounds (i.e., acoustic noise

Noise (acoustic)

Acoustic noise is any sound in the acoustic domain, either deliberate or unintended. It is important to recognise that the term "noise" is also used to refer to other, non-audible forms, especially in electronics and in the radio/radar spectrum.-Environmental noise:Environmental noise is the...

) by means of active noise control

Active noise control

Active noise control is a method for reducing unwanted sound.- Explanation :...

 (ANC). This involves using one or more microphones placed near the ear, and electronic circuitry which uses the microphone signal to generate an "antinoise" signal. When the antinoise signal is produced by the speaker driver

Speaker driver

A speaker driver is an individual transducer that converts electrical energy to sound waves, typically as part of a loudspeaker, television, or other electronics device. Sometimes the transducer is itself referred to as a speaker, particularly when a single one is mounted in an enclosure or as...

 in the headphone, destructive interference cancels out the ambient noise as heard within the enclosed volume of the headphone.