Audio Signal to Noise
From Zanecorpwiki
Signal to noise the measure, in decibels, between the background noise produced by a component, usually an amp, and the actual signal output. Though given at one number, the S/N will vary with input frequency and volume, and while most equipment will probably use similar inputs to the test, there is no hard standard.
The test goes something like this: with zero input, how much output comes out of the amp? This is the noise floor and represents noise generated by the electronic components. The difference between that and the strength of the output signal at a given alignment level is the signal to noise. Anything above 110dB is going to be pretty good and would mean that the noise would be undetectable to the human ear under most circumstances.[1]
You're best bet in hearing noise is going to be in very soft parts of the music, like a very quite lead in or a break in a classical piece. Even here, you have to consider that background noise is usually 35dB and the dynamic range of the human ear is about 130dB, so with an S/N of 110dB+, any noise in your audio component is going to be smothered by even very soft background noise. S/N better than 110dB is only useful if you're in the habit of listening to very soft music while sitting motionless and holding your breath in a room with thickly padded walls...
