Signal to Noise Ratio

I'll take a stab at this. Let's say the signal is only the charged particles (the music on the tape) and the noise is the scraping of the tape over the heads. Everything else in environmental, mechanical, electrical and radio contact with the signal is making noise too but forget about it for simplicity. Ok now imagine making salad dressing. Just olive oil (levels of charged particles) and vinegar (levels of noise). One rides atop the other. In real life they're mixed up, but in a visual sense the signal dominates the noise and rides above it. Ok? Now let's say the whole bottle is filled with dressing to a level called 0dB. How far down (from loud to soft) into the oil can you go until you hit the vinegar? The signal-to-noise ratio tells you. For example, if the ratio is 60dB, you'll hear all the signals that occur from 0dB (the loudest reference) all the way down to 60dB less loud than that. Softer than that, the noise will overcome the signal and obscure its perception. Good luck!

That is slightly different from my understanding. The term Signal to Noise Ratio is just that, a ratio. My understanding is that the idea is a 100S/N ratio means that for every 100 dB's of signal, you get 1dB of noise. Thus you want as much signal as possible for every bit of noise.

JUST GET A DBX ENCODE/DECODER OR BUY A CASSETTE DECK THAT HAS DOLBY S AND FORGET ABOUT IT. THAT IS ABOUT 85 ON THE SCALE OF SIGNAL-TO-NOISE RATIO.CD'S HIT AROUND 90.

Most of the info already posted is essentially correct, save a few points. S/N ratio is a bit of misnomer, although it obviously expresses a relationship between the input audio signal and the noise inherent in the system (the electronics primarily, but "dirty" electricity can also contribute). To be a bit more precise, the noise in the system is best expressed as a "minus" figure below the signal. Hence, a S/N ratio of -96 db (pretty typical for CD's) means that the noise level is 96 db below the audio signal. The higher the S/N ratio number, (e.g., -100db), the lower the noise level in relation to the signal level. Some of the newer power amps, such as Bryston's 4B-ST, now have S/N ratios around -116 to -118 db, so they are actually quieter than CD's. The S/N ratio really becomes a factor when you are listening to very quiet music, since this is the time when it is most likely for the noise to be audible. On loud musical passages, such as heavy metal rock, the S/N ratio is essentially unimportant. Likewise, very weak audio signals, such as those from a low output phono cartridge (which can be less than 1.0 mv), may be affected by the noise. Hence, S/N ratio can be a significant factor in reproducing sound from LP's. Hope this helps.