Noise Floor and Signal-to-Noise Ratio: What They Mean for Your Recordings
Every recording contains some background noise: the room, the air conditioner, the microphone itself. Two measurements describe how much of a problem it is.
The noise floor
The noise floor is the level of the background when nobody is speaking. It is measured in dBFS, a scale where 0 is the loudest value a digital file can hold and quieter sounds are negative numbers. A noise floor of -60 dBFS is quieter than one of -40 dBFS.
You can estimate it from the pauses between sentences: look at how loud the file is when only the room is audible.
Signal-to-noise ratio (SNR)
SNR compares your voice with the noise: the speech level minus the noise floor, in decibels. If the speech sits at -20 dBFS and the noise floor at -60 dBFS, the SNR is 40 dB.
What numbers are good?
There is no universal rule, and projects set their own limits. As a rough guide for speech:
- Above 40 dB: very clean.
- 30 to 40 dB: good for most work.
- 20 to 30 dB: usable but noticeable; many projects reject it.
- Below 20 dB: noisy; hard to transcribe and hard to clean up.
How to improve it
- Reduce the noise at the source. Turn off fans and air conditioners, close windows, and choose a room with soft furnishings. See recording clean audio with a phone.
- Get closer to the microphone (about 15 to 20 cm). Your voice gets louder while the room stays the same, so SNR rises.
- Do not rely on amplifying afterwards. Raising the volume of a finished file raises the noise by the same amount. SNR does not change.
- Be careful with heavy noise reduction. It can make speech sound watery. Prefer a clean recording to a "repaired" one.
Measure it for many files
The Sayvoi quality checker estimates each file's noise floor from its quietest parts and its SNR, then flags the files that fall below the limit you set. You can read more in our pre-delivery checklist. The numbers are estimates from the audio itself, so listen to a few files as well.
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