So I understand the basic principles behind noise cancellation. You essentially use a microphone to record incoming sound waves and create an inverse wave that destructively interferes with the initial wave, thus, cancelling it out. But I don’t understand, practically, how this is done.
Let’s assume the sound wave makes contact with the microphone in the AirPod, which analyses the wave and shoots out an inverse wave, but by that point – the initial sound wave would surely have already reached my ears. The AirPod basically needs to cancel the sound wave before it moves roughly a centimetre or it’s too late.
The speed of sound (in a standard environment like air) is 343 meters per second or 34,300 centimetres per second; this means the AirPod has 1/34,300 seconds or ~0.03 miliseconds to do these operations to cancel the wave. That just seems absurd to me for such a tiny chip in the bloody AirPod.
Someone fix my confusion please.
In: 678
This is why noise cancellation works better on low-frequency sounds than high-frequency. Typically they work best on frequencies lower than [1000 Hz.](https://www.nytimes.com/wirecutter/blog/what-noise-cancelling-headphones-do/) — that’s 1000 times per second. The electronics must detect the sound and create a cancelling audio waveform faster than that — say, 10,000 or 50,000 audio measurements per second.
I can’t find technical specs for the microprocessor in AirPods, but it’s quite common for embedded chips like these to have clock speeds of 10 or 50 *million* code operations per second. Which means they have time to do on the order of 1000 code operations per audio measurement.
Which is plenty.
Point is, sound is fast, but computers are faster.
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