Have you ever wondered… how noise-cancelling headphones work?
It wouldn’t be an exaggeration to regard noise cancelling headphone a game-changer of recent times. Whether you’re on a plane, in a subway or on a crowded street, noise-cancelling headphones will drown out almost everything around you, bringing peace and quiet to your ears. But how do they work? To enable such a feature, your headphones must have the ability to listen as well — to everything around you. We will refer to these sounds as ambient sounds from hereon.
Sound is made up of waves and as it moves through the air, it compresses and expands the air in repeated patterns. Each sound wave is different, comprising of peaks and troughs that correspond to the regions of compression and expansion of air. Active noise-cancelling headphones utilize this physics of sound waves and their ability to cancel each other out (in a phenomenon called destructive interference) to get rid of the ambient sounds. Destructive interference is when a second sound wave, equal but opposite, combines with the first one. When these two opposing patterns stack on top of each other, compressions unstretch the expansions and expansions unbunch the compressions, resulting in air that is neither stretched nor compressed. Noise-cancelling headphones, thus, have their own microphones that detect ambient soundwaves and create opposing waveforms. The waves cancel each other out, and a flat line ensues in form of blissful silence!
It is worth mentioning, however, that noise-cancelling technology may not be able to get rid of all outside noise every time. While the feature works effectively in the presence of consistent noise (let’s say, the noise of a subway train), some sounds (like the sudden honking of a car) may still be heard. This is because sounds that are sudden or change frequently in pitch are more difficult for the device to react to and cancel in time. You can only eliminate so many sounds at once, and perfect silence may be difficult to achieve every single time (contrary to what is suggested in advertisements).
