Signal to Noise Ratio
One of the biggest battles we face as audio engineers is unwanted noise. The original sound source is pure, and we want to capture it as pure as possible, however it immediately becomes contaminated with noise from the environment, noise from the microphone electronics, and static from the preamps and converters. We are always trying to keep the signal as pure as possible, with as little noise as possible. This is called the signal to noise ratio. Every link in the audio chain adds noise somehow, but generally, better quality gear adds less noise. It’s quite noticeable in consumer grade preamps, if you are using a microphone which requires a lot of gain. As you turn the gain up, you can hear static noise that gets louder. If the source you are recording is fairly quiet, the recording will be contaminated with a lot of this static noise, and as you bring this part up in a mix, you will also be raising the amount of noise, which will mask all the other parts in the mix.
The louder the source is that’s being recorded, the more it will rise above the static noise, and therefore give you a better signal to noise ratio.
As I’ve stated in my philosophy, noise is the killer, so optimizing the signal to noise ratio is something we always want to take into consideration.