What Is Signal-to-Noise Ratio in Audio?

What is signal-to-noise ratio? It compares how loud the wanted sound, such as a voice, is against the background noise, usually in decibels. A higher ratio means the voice stands out more. Every 10 dB step is a tenfold change in power.

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Key facts

Equal power for voice and noise gives a ratio of 0 dB, and a ratio below zero means the noise is louder than the voice.
The ratio is about the difference, not the volume: turning the whole recording up raises voice and noise together and leaves the ratio unchanged.
Noise can be a fan, traffic, room echo or the hiss of a cheap microphone, and all of them lower the ratio.
The most effective fix is at the source: move the microphone closer to the speaker, since the voice then gains while the room noise stays put.
Software noise reduction can lift the ratio a little but may also remove quiet speech sounds, so it is not a cure for a poor recording.

What it looks like

// formula
// snr_db = 10 * log10(signal_power / noise_power)

// worked values
// 100 to 1 power ratio  ->  20 dB
// 10 to 1 power ratio   ->  10 dB
// 1 to 1 power ratio    ->   0 dB

// check levels in a file
ffmpeg -i room.wav -af volumedetect -f null -

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Frequently asked questions

What is a good signal-to-noise ratio for speech?

A higher number is better and there is no single cut-off. As a rule, if you can hear the noise clearly while the voice plays, the ratio is too low.

How is the ratio calculated?

It is ten times the base-ten logarithm of voice power divided by noise power. A power ratio of 100 to 1, for example, gives 20 dB.

Does turning up the volume fix a noisy recording?

No. Voice and noise rise together, so the ratio stays the same. Re-recording closer to the speaker is the real fix.

Will noise hurt a transcript from the Potok bot?

Heavy noise can hide quiet words and cause errors. Review names and numbers closely when the source recording is noisy.

How can I measure it on a file?

A simple check is to compare the level of a speech section with a silent section. Editors and the volumedetect filter in ffmpeg report levels.

Sources

Each source was opened by hand on the date shown. Pages change, so open the source if a detail matters to you.

Signal-to-noise ratio (Wikipedia), Wikipedia · checked 2026-10-18
Background noise (Wikipedia), Wikipedia · checked 2026-10-18

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