Remove background noise. Hiss, hum, fans, air con.

At a glance

How it actually works

The recording is chopped into short overlapping frames and each one is converted into a frequency spectrum — a measurement of how much energy sits in each frequency band at that instant. Steady noise has a distinctive signature in that view: it is present in every frame at roughly the same level, because a fan does not stop humming between your words.

The tool estimates that floor by taking a low percentile of each frequency band across the whole file, then goes back through and attenuates any band that sits close to it, leaving louder content untouched. Speech and music, which are far above the floor when present, come through; the constant hum underneath is pulled down by 9 to 24 dB depending on the strength you choose.

The attenuation uses a soft knee rather than a hard cut. A hard gate produces the warbling, underwater artefact that people associate with badly denoised audio — sounds flickering in and out as they cross the threshold. Easing between attenuated and untouched avoids most of that.

What it fixes, and what it can't

It fixes steady noise. That means anything continuous and unchanging: computer fans, air conditioning, refrigerator hum, the 50 or 60 Hz buzz from bad grounding, tape hiss, the hiss of a cheap preamp or a phone microphone turned up too far. These are the things that make an otherwise fine recording sound amateur, and they come out cleanly.

It cannot fix irregular noise. A cough, a door closing, a car passing, a chair creaking, someone else talking in the background — none of these are stationary, so there is no consistent floor to estimate and nothing for a spectral gate to grip. Removing those requires source separation, which is a fundamentally different and much harder problem.

This distinction is worth understanding before you spend time on settings. If your recording has a hum, this will fix it. If your recording has a dog barking, nothing here will help and you will need to cut around it.

Choosing a strength

Medium is the right default for speech and handles most room tone and fan noise without touching the voice.

Gentle is the setting for music. Music occupies far more of the spectrum than speech does, including quiet passages that a more aggressive gate would mistake for noise — reverb tails, cymbal decay and the quiet end of a fade are all vulnerable. Gentle removes less noise but is much less likely to dull the recording.

Strong is for recordings that are genuinely noisy: a phone recording in a busy room, an old tape transfer, a video call capture. Expect some cost to the voice — a slightly hollow or processed quality — because at that level of reduction you are removing content that overlaps with the noise.

A useful order of operations: remove the silence first if the recording has long gaps, denoise second, and normalize last. Denoising lowers the overall level, so normalizing afterwards puts it back where you want it.

What you lose

Some high-frequency detail, always. Hiss and the top end of a voice occupy the same region of the spectrum, so pulling one down inevitably takes a little of the other. On speech this reads as very slightly duller and is almost never a problem; on music it is more noticeable, which is why Gentle exists.

Processing time. This is the slowest tool on the site by some margin — the file is transformed to the frequency domain, modified, and transformed back, twice over, and a long recording means a lot of frames. A three-minute file takes a few seconds; a one-hour interview takes a while. The progress bar is real.

You do not lose the original. Denoising is destructive in the sense that the output is a new file, so keep the source until you have listened to the result — particularly on music, where it is worth comparing the two before committing.