Sampling and frequency information
The human ear can typically hear frequencies up to 20kHz = 20,000 Hz. The Shannon-Nyquist sampling theorem states that to reconstruct a signal, we need to sample it at at least twice the highest frequency content of the signal. Thus, to reconstruct a sound with a frequency of 20kHz, we would need to sample at a rate of 40kHz.
In audio engineering, we typically use a sample rate of 44.1kHz instead of 40kHz as that was the standard that fit video during that time.[1]
References:
[1]: watkinson-1998 p.228