The fidelity of
audio is a measure of how closely it approximates the
real sound that the recording is a reproduction of. Alternately, such as at a
live concert, the fidelity of the sound is a measure of how closely the sound coming out of the
speakers mimics that coming out of the
singers and
instruments.
Casual research (ie. one
google search) indicates that there is no set
standard or
unit by which fidelity is measured. Hence, we can all slap the term '
high fidelity' onto our
shoddy stereo products. "It's okay
honey, it's HIGH fidelity!"