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Some sampling rates are more popular than others, for various reasons. Some recording hardware is restricted to (approximations of) some of these rates, some playback hardware has direct support for some. The popularity of divisors of common rates can be explained by the simplicity of clock frequency dividing circuits :-).
Samples/sec Description
5500 One fourth of the Mac sampling rate (rarely seen).
7333 One third of the Mac sampling rate (rarely seen).
8000 Exactly 8000 samples/sec is a telephony standard that
goes together with u-law (and also A-law) encoding.
Some systems use an slightly different rate; in
particular, the NeXT workstation uses 8012.8210513,
apparently the rate used by Telco CODECs.
11 k Either 11025, a quarter of the CD sampling rate,
or half the Mac sampling rate (perhaps the most
popular rate on the Mac).
16000 Used by the G.722 compression standard.
18.9 k CD-ROM/XA standard.
22 k Either 22050, half the CD sampling rate, or the Mac
rate; the latter is precisely 22254.545454545454 but
usually misquoted as 22000. (Historical note:
22254.5454... was the horizontal scan rate of the
original 128k Mac.)
32000 Used in digital radio, NICAM (Nearly Instantaneous
Compandable Audio Matrix [IBA/BREMA/BBC]) and other
TV work, at least in the UK; also long play DAT and
Japanese HDTV.
37.8 k CD-ROM/XA standard for higher quality.
44056 This weird rate is used by professional audio
equipment to fit an integral number of samples in a
video frame.
44100 The CD sampling rate. (DAT players recording
digitally from CD also use this rate.)
48000 The DAT (Digital Audio Tape) sampling rate for
domestic use.
While professional musicians disagree, most people don't have a problem if recorded sound is played at a slightly different rate, say, 1-2%. On the other hand, if recorded data is being fed into a playback device in real time (say, over a network), even the smallest difference in sampling rate can frustrate the buffering scheme used.
There may be an emerging tendency to standardize on only a few sampling rates and encoding styles, even if the file formats may differ. The suggested rates and styles are:
rate (samp/sec) style mono/stereo
8000 8-bit u-law mono
22050 8-bit linear unsigned mono and stereo
44100 16-bit linear signed mono and stereo
