How Do Noise-Cancelling Earbuds Work?

Active noise cancellation (ANC) relies on the physics of destructive interference. External microphones on the earbuds sample ambient noise hundreds of times per second. A digital signal processor (DSP) analyses the incoming sound wave and generates an "anti-noise" signal — a sound wave of equal amplitude but opposite phase (inverted by 180°). When the anti-noise meets the original noise inside your ear canal, the peaks and troughs cancel out, effectively reducing the perceived sound. Feed-forward ANC uses only external mics; feedback ANC uses an internal mic to monitor what you actually hear; hybrid ANC combines both for best performance. Modern ANC earbuds can reduce low-frequency noise (like airplane engines) by up to 30–40 dB.