Genesis Technologies Digital Lens Dither & Jitter  Sidebar 3:
Dither & Jitter  Dither: If you think about the literal meaning
of the word dither—"a confused or agitated state"—you're halfway
to understanding how dither works in digital audio. Dither is a
small amount of noise added to the signal that makes digital
behave (and sound) more like analog. This noise allows a digital
system to resolve low-level information below the amplitude of
its Least Significant Bit (LSB). Without dither, signals with
amplitudes below the LSB are simply ignored by the quantizer;
the signal never traverses two quantization steps, a requirement
of encoding the signal. The small amount of dither added to the
signal causes the wanted audio signal to traverse quantization
steps and thus be encoded with more fidelity to the original
waveform. The dither "agitates" the tiny audio signal so that
the quantizer becomes "confused" about which quantization level
the signal is hovering near, causing it to vacillate between two
quantization