A noise-canceling microphone
is a microphone
designed to filter out ambient noise
from the desired sound, especially useful in noisy environments. This technique often uses two or more microphones and circuitry to remove the noise. The primary microphone, a unidirectional mic, is directed at the desired source (like a person's mouth). A second mic pointed in another direction receives ambient noise. In a noisy environment, both microphones receive noise, but only the primary mic receives the desired sounds.
The internal electronic circuitry of a noise-canceling mic compares the noise signal with the signal from the primary, directional microphone. The circuit may employ passive or active noise canceling techniques to filter out the noise, producing an output signal that has a lower noise floor and a higher signal-to-noise ratio.