Hello and welcome to this week's article!
This article is to be considered an expansion of our Gain Staging article (click here to read it), in which I would like to elaborate more about the signal to noise topic.
When we record an audio sound (regardless of whether we're using an old analog tape recorder or a modern digital workstation) we are actually capturing certain frequencies, those that are audible from our microphone, and putting them into a "corridor" that has a floor and a ceiling.
If the recorded signal is too high it will "bump" into the ceiling and will distort, if it's too low it can become inaudible, therefore we need to find a level in which it can be heard properly without clipping.
This amplitude is controlled through the "Gain" knob of the preamplifier we're running through, and since we know that there is a "floor" and a "ceiling", there is also a sweet spot that we must find with the best signal-to noise ratio; the distance between the signal and the ceiling is called Headroom.
One thing that is important is that in the "corridor" I was mentioning, the floor is the level below which our preamp can't hear any sound, and this minimum level of signal (which is always present when recording, even if there is total silence) is called "noise floor", which is the lowest limit recorded from the source going into the preamp.
This noise floor can be pushed further down by changing the bit depth of the project, if the audio interface supports it: the higher the bit depth, the lower the ground noise level, but it can never be removed, and if after we have recorded a sound we realize it's too low and we increase the volume of that track in our DAW for example, we will increase more or less proportionally also the noise floor by the same amount of decibels (which is very bad).
How to calculate the signat-to-noise ratio = Signal Level MINUS Noise Level.
Example: the noise level peaks at -50db, the signal level peaks at -20db, the signal to noise ratio will be 30db (the distance between -50 and -20).
To sum it up, the lower we will set the input gain, the higher proportionally will be the signal-to noise-ratio, meaning that the related noise will be more and more prominent when we will turn the signal back up, so always make sure you are recording with the right input level, not too low to avoid the noise but not too high to avoid distortion: a good starting point for your DAW it's to set the projet to 24 bit and set the input gain of your audio interface so that the signal will peak at around -12db, this will give you enough headroom for the various further steps of the audio production.
I hope this was helpful!
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