As Doc Nomis said, the Nyquist Theorem states that if the sampling rate is more than double the maximum frequency you are trying to sample, then you can reproduce that sound perfectly. It doesn't matter if the frequency is 20 Hz or 20,000Hz, if you are sampling at 44.1kHz, then both frequencies get reproduced accurately. Each sample represents a point on a curve (not the height of a step) and the D/A converter recreates the curve as a continuous voltage wave.

There's a great video on this web page that explains almost all of the misconceptions about digital audio.

https://xiph.org/video/vid2.shtml