Remove background noise from audio

What it handles well, and what it does not

Octoolo uses FFmpeg's FFT noise reducer. It works out which part of the sound stays the same all the way through a recording, the noise floor, and lowers it, adjusting as that noise slowly changes. That makes it good at some noises and no help with others.

The noises on the right come and go, and to a noise reducer they look a lot like the voice you want to keep. Music is the one exception Octoolo handles, with a different tool: Separate voice and music lifts a voice out of the music behind it with AI on your PC. Other people talking, dogs and doors stay either way.

One strength, set for voices

There is no slider. The switch applies one moderate setting that lowers steady noise by as much as 18 decibels, enough to push hiss and fan noise well into the background of most voice recordings. It is moderate on purpose: noise reduction pushed harder starts to eat into the voice itself, which then sounds thin, hollow or as if it was recorded under water.

Expect a clear improvement, not silence. When the noise was almost as loud as the voice, some of it stays, and quiet word endings can soften a little. A recording with a low, even hum behind a clear voice is the ideal case; a phone held at arm's length in a windy street is not. If the cleaned version sounds worse to you, switch it off: the original is never touched, so trying costs nothing.

Listening for the difference

Noise reduction is easy to overrate on laptop speakers and easy to misjudge in a noisy office, so give it a fair test:

• Use headphones. Hiss and fan noise that speakers hide are obvious in them, and so are any side effects.
• Listen to the pauses. The gaps between sentences show how much noise has gone.
• Then listen to the voice. Check the “s” sounds and the ends of words. If they turn lispy or swirly, the noise was too close to the voice for a clean result.
• Compare at the same spot. Put the playhead on one sentence, play it with the switch on, then off.

Faint warbling or chirping in the pauses, sometimes called musical noise, means the reducer is working at its limit. In that case the honest fix is a new recording closer to the microphone; failing that, a slightly noisy natural voice usually sounds better than a clean, strange one.

A cleaner recording from the start

Noise reduction works far better on noise that was low to begin with, so a few minutes of setup pay off:

• The closer the microphone is to your mouth, the quieter the room sounds next to your voice.
• Switch off fans, heaters and anything else that hums, and record away from an open window.
• Curtains, a rug or a sofa soak up echo, which noise reduction cannot remove.
• Watch the meter in Record your voice: it should move well when you speak, without sitting at the very top.

Afterwards, switch on Even out loudness as well. Octoolo removes the noise first and evens out the loudness second, so the hiss is not raised along with the voice. A quick trim of the start and end finishes the job.