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This little article deals with how to convert a music piece to 22 KHz with as little damage as possible.

First of all, a simple formula. Detail limit of a sampled format is sampling frequency/8. In scientific sampling, a sampled signal is considered accurate as long as the sampling frequency is 8 times the frequency of the signal to be sampled. This is because 8 coordinates are required to describe a sine wave: 4 positive, 4 negative.

Hence, by the way, you need 160 KHz sampling to accurately represent 20 KHz (so much for CD audio's claims of "22 KHz bandwidth" - 22 KHz, yeah, but for noise, not music, detail limit is much lower).

Thus: 44100 Hz (CD audio) divided by 8=5512.5 Hz. Enough for midrange, but there's already distortion in the treble and high frequencies. 22050 Hz (Descent 3 sampling format for music) divided by 8=2756.25 Hz. Not very detailed, is it?

So what happens when you go over the magical f/8 limit? Aliasing happens. Rectification distortion, foldover, etc. Everything becomes "squarish" (or more precisely, triangular). The minimum time frame also becomes 0.36 msec., which is slow (to human perception that sounds "stiffy", "woody").

And that tends to sound weird. Get an acoustic instrument record and downsample to 22050 Hz, then listen to what happens to treble and space harmonics. But never fear, for there are ways to smoothing out the damage.