Noise remover: remove background noise from audio

How noise removal works

Background noise like hiss, a fan or an air conditioner is steady: it has roughly the same sound from one second to the next. That is what makes it removable. The tool first listens to the quietest moments of your recording, the pauses between words or the room before you start, and measures how loud the noise is at every frequency. That measurement is the noise profile.

Then it goes through the whole file in short overlapping slices, about 40 milliseconds each, and compares every frequency with the profile. Where the voice is much louder than the noise, it leaves the sound alone. Where there is little more than noise, it turns that frequency down. This is a Wiener filter, the classic method behind most noise reduction, with a few refinements from OBRA Mastering PRO: the decision follows the signal smoothly from slice to slice, and the gain is smoothed across neighbouring frequencies and over time.

That smoothing is what stops musical noise, the watery, chirping artefact that cheap noise reduction leaves behind. At the default strength the noise that remains is a softer version of the same hiss, not a cloud of little tones. Push the strength to the top and you will start to hear some of it, which is why the slider tells you when you are past the clean range.

Hum is different: it is a tone at 50 or 60 Hz, the frequency of the mains, plus its harmonics. The tool looks for that pattern, and if it finds it, it places very narrow notches on the hum and its first twelve harmonics. A 4 Hz wide notch takes out the buzz and leaves the voice around it untouched.

Automatic profile or a part you choose

Automatic works for most files: we build the profile from the quietest moments of the recording. If your file has almost no pauses, or the noise changes halfway through, choose From a selection and drag across a stretch where only the noise sounds. We suggest the quietest second of the file to start with.

Pick a stretch that is long enough, a second is plenty, and that has no breathing or speech in it. If you mark part of a word, the tool will think the voice is noise and remove some of it, which sounds hollow. Move the selection and listen again.

How to record cleaner audio

The cleanest noise is the noise you never record. Get the microphone closer to your mouth: a hand's width away gives far more voice for the same room noise than an arm's length. Turn off fans, the air conditioner and the fridge for the take, and move the laptop away from the microphone.

Record a few seconds of silence before you speak. It gives the noise remover a perfect profile. Keep the input gain so that your loudest words peak well below the top, around minus 10 dBFS, so nothing clips. Clipping and heavy reverb are not noise, and no noise reduction can undo them.

Soft rooms sound cleaner than bare ones. A closet full of clothes, a sofa, curtains or a duvet behind the microphone does more than any plugin. And if you hear hum, try another socket, unplug the laptop charger or use a different cable before you record.

Before and after: what to listen for

Listen to the pauses first: that is where the noise was loudest relative to the voice. With the default strength, steady hiss and fan noise drop by about 12 to 14 dB in our tests, which most people hear as the noise being gone in normal listening, while the voice keeps its level and its tone.

Then listen to the ends of words and the breaths. If they sound swallowed or metallic, the strength is too high for that recording: bring it down a little. If you are cleaning speech, Voice focus also makes the pauses quieter, which reads as cleaner on a phone speaker or in earbuds.

For a song or an instrument, keep Voice focus off: it cuts lows and highs that music needs.

Learn more, or get a person on it

Read the mastering guides, comparisons and data, or send your tracks to an engineer with OBRA ULTRA.