Booster Volume

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Short, plain-English explanations of the concepts behind volume and loudness. No mathematics beyond the occasional decibel, and no assumed background in audio engineering.

Where to start

You do not need any of this to use the tools — but a few ideas explain most of what people find surprising about volume. Why turning something up sometimes makes it worse. Why two tracks at the same measured level can sound completely different in loudness. Why a booster can offer 600% without falling apart, when doubling the numbers ought to distort immediately.

If you read only two pages here, make them what is loudness and what is audio clipping. Between them they cover the ceiling that limits every boost, and the reason perceived loudness and measured level are not the same thing.

The ideas these pages build on

Digital audio has a hard ceiling
Samples are numbers with a maximum value. Multiply past it and the peaks flatten, which is heard as crackle rather than as extra volume.
Loudness is perceptual, level is physical
Your ears respond to average energy weighted by frequency, not to the highest instantaneous peak. This is why the two so often disagree.
Every gain is a trade
Raising a signal raises its noise with it, and holding peaks down to make room costs dynamic range. Nothing here is free; the question is which cost you mind least.
Software cannot exceed hardware
Processing changes the signal handed to your speakers. It cannot make the amplifier stronger or the driver move further than it physically can.

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