GoKawiilActive noise canceling (ANC) uses a mix of passive sound isolation (blocking your ears), exterior microphones, and software to suppress environmental sounds before they reach your eardrums. The process, which has been refined since the late 1970s, involves sampling the sounds around you in real time (up to tens of thousands of times per second) and then neutralizing them.
To understand the process, we have to dig a little into physics. Sound moves through the air as pressure waves that eventually hit your eardrums. The frequency of a wave is the number of times it oscillates per second, and frequency determines pitch. So we perceive a low-frequency wave, like from an airplane rumble, as a dull bass sound. And a high-frequency wave, like from a siren or a yapping dog, we hear as a sharp treble sound.
What noise-canceling systems do is they perceive the frequency of a sound wave and instantly generate a polar opposite waveform: When one wave is at its peak, the other will be at its trough, and vice versa. Adding those waves together, they zero each other out, as if there is no wave at all.
The difficulty is that there are often many sounds at once, and each contains a mix of different frequencies, so it’s hard to quell all the sounds in your environment. But through a combination of faster processing, better microphones, and effective blocking of our ear canals, the latest earbuds and headphones are getting impressively close.