How to clean up a recording: background noise, hiss, clicks and reverb
3 min read · Updated
A good recording spoiled by room noise, electrical hum or clipping can often be rescued very well, as long as each problem gets the right tool in the right order. Here is the method, from diagnosis to fine repair.
In short
- Identify the problem precisely before choosing a tool.
- Repair in order: clipping, clicks, hum, background noise, reverb.
- Listen to what is removed, not just the result.
- For spoken word: suitable denoising, breaths and plosives.
- Cut noise between phrases with a gate.
- Fix one-off accidents on the spectrogram.
- Stop before the voice sounds "underwater".
Identifying the problem
Each flaw has its signature. Hiss and fan noise form a continuous bed in the highs and mids. Hum is a steady low note at 50 Hz (Europe) or 60 Hz (North America), with its harmonics. Clicks are very short impulses. Clipping flattens the peaks and hardens the sound. Room reverb stretches every word.
Listen to a passage without voice (between two phrases): what you hear there is the noise to remove. A spectrum analyzer or a spectrogram confirms what your ear suspects.
The repair order
Order matters, because each process changes what the next one sees: fix clipping first (de-clip), then clicks (de-click), hum (de-hum), background noise (denoise) and finally reverb (de-reverb). Denoising a clipped or click-ridden signal gives worse results.
Repair AI follows exactly this order, with its five modules in series; with all of them off, the signal comes out bit-identical to the original.
Listening to what you remove
The denoising trap is listening only to the result: the ear adapts and you push too far. Listen instead to what is being removed (the LISTEN function on every Repair AI and Clarea module): if you hear pieces of voice, consonants or instrument attack in it, back off.
Compare often with bypass, at equal loudness, on an excerpt that contains both voice and silence.
Spoken word: podcast, voice-over, interview
Spoken word often stacks several problems: room noise, low rumble, loud breaths, "p" and "b" sounds blowing into the mic, uneven level. Clarea chains six modules built for it: rumble filter, AI denoising running on your machine, de-reverb, breaths, plosives and a leveler that follows the voice without raising the pauses.
Processing runs in the DAW, with no connection and without sending your audio anywhere. Its latency of about 100 ms is compensated by the DAW: it is a mixing and post-production tool, not for live monitoring.
Cutting noise between phrases
When noise only bothers you in the silences, a noise gate (or a gentler expander) is enough: it turns the sound down below a threshold, between phrases, between drum hits or when an amp is not playing. Set the threshold just above the noise, a fast attack and a release long enough not to chop word endings.
Gatea offers both behaviors, gate or downward expansion, with a threshold from -90 to 0 dB.
One-off repairs on the spectrogram
A cough, a phone ring, a creaking chair, an isolated click: these accidents are not fixed with continuous processing. On a spectrogram they show up as a well-defined spot you can select and attenuate without touching the rest.
Repair AI's Spectral Repair tab lets you select the area with a rectangle, a lasso, a time range or by harmonics, then erase it.
Don't overdo it
Overly aggressive denoising leaves artifacts: metallic sound, "chirping", a voice that seems underwater. Better to keep a slight natural noise floor than a damaged voice; in a mix or under music, a little residual noise is barely audible.
And for the next take: mic closer to the source, a deader room (curtains, blankets), noisy devices off. Five minutes of preparation saves an hour of repair.
Frequently asked questions
- Can you remove room echo from a voice?
- Largely, with a de-reverb, especially if the voice was fairly close to the mic. Very strong reverb cannot be fully erased without artifacts: reduce it rather than trying to remove it.
- Does denoising work in real time?
- Yes, denoiser plugins process sound during playback. The most effective ones have a small latency (about 100 ms for Repair AI and Clarea), compensated automatically by the DAW.
- How do I remove electrical hum?
- With a de-hum set to 50 Hz in Europe or 60 Hz in North America: it removes the fundamental and its harmonics without hollowing out the rest of the low end, far better than a simple low cut.
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