Basically just looking into external mics for my phone and all the reviews for the different products I’m looking at are talking about “too much gain” and “not enough gain” and I have no earthly idea what that means. I tried looking it up, but it’s confusing as hell for someone with no know, who just wants to record concerts to listen to again later
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The programming in microphones will cut off certain frequencies or noise in order to get a clearer recording. “Gain” changes how much is filtered. With less gain only more pure tones are recorded. With more gain, you get the noise as well.
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AFAIK (not an audiophile), but gain refers to the amount of sound energy the microphone translates into signal for recording or re-processing through the remainder of the audio equipment. Take your voice as an example and keep your personal volume exactly the same at each attempt. Turn the gain up too high and the mic will pick up your breathing, the compression of your lips when you close your mouth or even your beard hairs jiggling against one another. Turn the gain too low and you’ll sound like you’re at the other end of a large room (or worse, not be detectable at all)
Gain refers to how much signal the microphone picks up.
High gain means it will detect more sound (in a wider area around the mic) but also increase the chance of audio feedback.
Low gain means you have less chance of feedback, but some sounds may not register in the mic (or in a smaller area around the mic)
An audio signal is just a measure of changes in air pressure. But there’s no real limit to how big those changes in air pressure can be. Imagine putting your ear or a microphone up against a nuclear bomb, for instance.
Similarly, when you try and take those pressure waves and convert them into a voltage that can be processed electronically, the voltage that you would get from a (presumably indestructible) microphone capable of picking up the sound of a nuclear blast would likely be in the millions of volts. Any audio engineer trying to deal with a signal like that would find themselves electrocuted to a crisp trying.
So when we try and measure or record an audio signal, we have to deal with the practical reality around the range of voltages we can meaningfully process. A typical microphone will convert sound waves from speech into voltage waves of around 1-100 millivolts.
But you’ll want to use microphones to pick up different kinds of sounds. For instance, you might in one setting want to hear two people whispering, and then in another setting you’ll want to capture a gunfight. If you were to just record the raw voltages coming out of the microphone for each of these situations, you might find the whispers are too quiet to do anything useful with, and the gunshots are so loud that the sound waves push the microphone outside the voltage range it’s allowed to produce, resulting in “clipping”.
You can fix this electronically by scaling the voltage up or down so that both the whisper and the gunfight both end up producing similar voltage ranges. This maximizes the fidelity of the sound captured, so that a whispered conversation can be intelligible and the gunfight captures the full range of sounds.
This factor that you apply to the voltage in order to scale it like this is called gain.
There’s also a digital version of this. Once voltages are processed by a computer, they’re just turned into numbers. But in a computer, numbers have a fixed degree of precision, and often range. So a mathematical scaling can be used to add or remove gain once it’s in the digital form as well.
imagine you are speaking into a megaphone
it amplifies your voice to sound like 100 times louder right? that’s gain
your voice ‘gained’ volume
To ELI5 think of gain as a bubble around a microphone that indicates the area the microphone will pick up sound most efficiently. When you adjust the gain, you are making the bubble bigger or smaller.
“Gain” in this context means amplification of the output of the system. It’s usually expressed in decibels, which is a logarithmically scaled ratio of the output to the input.
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