Noise-cancelling Headphones

Noise-cancelling headphones are headphones that reduce unwanted ambient sounds (i.e., acoustic noise) by means of active noise control (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 in the headphone, destructive interference cancels out the ambient noise as heard within the enclosed volume of the headphone. They should not be confused with noise isolating headphones.

Noise cancellation makes it possible to enjoy music without raising the volume excessively. It can also help a passenger sleep in a noisy vehicle such as an airliner. Research examining the benefits of noise cancelling headphones in the aviation environment has found that compared to passive noise attenuating headphones or no headphones, noise cancelling headphones significantly increases the signal to noise ratio, making hearing important information such as safety announcements easier. The benefits of noise cancelling headphones also extend to situations involving concurrent task (dual task) performance such as completing a math based task (e.g., Sudoku) as well as listening task.

Noise-cancelling headphones typically use ANC to cancel the lower-frequency portions of the noise; they depend on more traditional methods such as soundproofing to prevent higher-frequency noise from reaching the ear. This approach is preferred because it reduces the demand for complicated electronic circuitry that would be required for noise cancellation at higher frequencies, where active cancellation is less effective. To truly cancel high frequency components (coming at the ear from all directions), the sensor and emitter for the cancelling waveform would have to be adjacent to the user's eardrum, which is not technically feasible.