Hacker News Reader

CDs use 44.1kHz because your sample rate needs to be double the highest frequency you want to encode to avoid aliasing artifacts: https://en.wikipedia.org/wiki/Nyquist%E2%80%93Shannon_sampli...

20kHz is the top of the human hearing range, and picking something a little bit higher than 40kHz gives you room to smoothly roll off frequencies above the audible range without needing an extremely steep filter that would create a large phase shift.

View on HN

You do in fact need an extremely steep filter. 44.1kHz is a little over an octave above 20k, and for adequate filtering and reconstruction you need 96dB of roll-off at at 16-bits and 144dB at 24-bits.

It's practically impossible to design an artefact-free filter with a roll-off as steep as that. Every single person who says that 44.1k is enough "because Nyquist" has failed to understand this.

You can trade off delay against various artefacts, including passband ripple, non-linear phase smearing, and others. But the shorter the delay, the less true it is that you get out exactly what you put in.

In practice, artifacts become common past something like 16 kHz. I'm not sure how much of this is math and how much is that almost all speakers are made very cheaply.

Reply on news.ycombinator.com