noisecanceling

Noisecanceling, or active noise control, refers to methods that reduce unwanted sound by generating an anti-noise signal that interferes destructively with the original noise. It is commonly contrasted with passive noise cancellation, which relies on physical barriers such as ear cups, padding, or enclosure walls to block sound. Many systems use a combination of both approaches in a hybrid arrangement.

An noisecanceling system typically includes microphones to sense ambient noise, a signal processor to generate an inverse waveform, and actuators such as speakers to emit the anti-noise. The processing often relies on adaptive filters, such as finite impulse response or least-mean-squares algorithms, that continuously adjust the anti-noise to match changing noise conditions. Configurations are described as feedforward, feedback, or hybrid: feedforward systems sense noise before it reaches the listener, feedback systems monitor residual noise after it has been produced, and hybrids combine both sensing strategies.

Performance characteristics show noisecanceling is most effective at low frequencies, where sound wavelengths are long and cancellation can be achieved with relatively small phase shifts. High-frequency cancellation is more difficult due to rapid phase variations, arriving noise from multiple directions, and practical limits on sensor and processor latency. Limitations include wind noise, occlusion effects from ear molds or headphones, power consumption, and occasional distortion of desired sounds if the control loop is poorly tuned.

Applications span consumer headphones and earbuds, aviation headsets, automotive and industrial environments, and room or cabin installations. The technology aims to improve comfort and perceived loudness, particularly in consistently noisy settings, by reducing the need for large passive barriers.