Audacity noise reduction: how to remove background noise
To remove background noise in Audacity 4, select half a second of noise-only audio, open Effect ▸ Noise removal and repair ▸ Noise reduction and click Get noise profile. Then select the whole track, open the same effect again and apply it. For noise that changes from second to second, add a denoiser plugin in the realtime effects panel instead; it needs no noise profile.
This guide covers the built-in Noise reduction effect step by step, what its sliders do and where to start them, and the noises it cannot fix. It then covers denoiser plugins that run live in Audacity 4, the OpenVINO AI route that still needs Audacity 3, and the difference between reduction and a noise gate.
Tested on Audacity 4.0.1 on macOS Sequoia; the screenshots are from that install. Shortcuts are written for Windows; macOS uses Cmd where Windows uses Ctrl. Where Audacity 3 differs, a short note says so.
Noise reduction for Audacity
Three routes at a glance:
- Steady hiss or hum, with a moment of silence to sample: the built-in Noise reduction effect. Free, applied once to the waveform.
- Noise that comes and goes, or no clean moment to sample: a denoiser plugin in the realtime effects panel. It runs live, with nothing to profile.
- Speech, if you still run Audacity 3: OpenVINO AI Noise Suppression. Free, needs no profile, and not available in Audacity 4 yet.
The fast fix: built-in Noise reduction in three steps
Audacity’s Noise reduction learns your noise from a sample of it alone, then subtracts it. Skipping that sample is why the effect often appears not to work.
In Audacity 4 it is a destructive effect. Applying it changes the recorded waveform, and undo (Ctrl+Z) reverses it. It is not in the realtime effects panel, which holds plugins. The Effect menu’s Noise removal and repair submenu lists Click removal, Noise reduction, Repair, Clip fix and Noise gate, in that order.
- Capture the noise profile. Select at least half a second where only the unwanted noise is audible. Open Effect ▸ Noise removal and repair ▸ Noise reduction and click Get noise profile. The dialog closes; Audacity has stored the noise.
- Select the audio to clean. Usually the whole track, with Ctrl+A.
- Apply the effect. Open Noise reduction again, press Preview to listen, then click Apply.
The dialog follows the same order. Step 1 holds Get noise profile, and Step 2 holds the sliders and Output. Preview and Apply stay greyed out until a profile exists.
On Audacity 3 the procedure is the same; the labels are written in title case, such as Get Noise Profile.
Getting the noise profile right
Find the cleanest noise you can. Look for a flat stretch in the waveform, such as the beginning before you started talking or a pause between sentences. If a chair creaks or a breath lands in your selection, Audacity learns that as noise and will attack similar frequencies in your voice. Room noise shows as a thin, even band next to the first word.
Half a second is the minimum. A second or two gives the analysis more to work with.
Profile each recording separately. The room, the fan and the traffic change from day to day, so a profile from Tuesday does a worse job on Wednesday’s file.
Start every recording with five seconds of silence. It costs nothing and guarantees a clean profile later. If you record regularly, this habit improves your results more than any slider. Recording computer audio in Audacity shows where that silence goes when the source is a call or a browser.
What the three sliders do
Audacity 4 opens the dialog at 6 dB of reduction, Sensitivity 6 and Frequency smoothing 6 bands, a sensible place to start.
Noise reduction (dB) sets how much the profiled noise is turned down, from 0 to 48 dB. This is the slider to be careful with, because pushing it is what produces the artifacts below. Increase it only until the noise stops bothering you, not until it disappears.
Sensitivity sets how readily Audacity counts a sound as noise. Raise it and more of the signal is treated as noise, which cleans harder and eats into the voice sooner.
Frequency smoothing spreads the reduction across neighboring frequency bands, from 0 to 12. Raising it is the main fix for the metallic ringing described below.
Output is the control most guides miss. Switch it from Audio with noise removed to Noise only and preview to hear exactly what is about to be taken out. If you can make out words in there, the settings are too aggressive. Switch back before you apply. The Noise reduction page of the Audacity manual lists every range and default.
The three sliders interact and the right settings differ per recording, so preview often and compare with the untreated audio.
When it goes wrong
Both failure modes come from asking for too much.
Watery or underwater voice. Push Noise reduction too far and the voice turns warbling and hollow, because the effect is now removing parts of the speech along with the noise. Back the reduction off. A little audible hiss under a natural voice sounds more professional than a silent background with a robotic voice on top.
Musical noise. At aggressive settings you hear faint tinny or metallic artifacts, often described as ringing or chirping. Raise Frequency smoothing and they soften.
Aim to reduce noise until a listener stops noticing it, not to eliminate it. Total removal always costs voice quality.
What noise reduction cannot fix
The effect is built for constant noise, such as fan hiss, air-conditioning rumble, a fridge hum, electrical whine and buzzes. It is the wrong tool for four problems.
One-off clicks, pops and bangs. A door slam or a mouth click is not in the profile and will not be touched. Cut them out, or select the short stretch and use Click removal or Repair from the same Noise removal and repair submenu.
Room reverb. Echo from a hard, empty room is your own voice arriving late, and noise reduction cannot tell it apart from the voice. No free tool fixes this well; treat the room or get closer to the microphone.
Intermittent noise. A passing motorbike, a dog, someone talking in another room. These vary, so a static profile does not match them. This is the job for a realtime denoiser, next.
Clipping and distortion. Audio recorded too loud stays distorted. Re-record it.
The realtime route: a denoiser plugin on the track
In Audacity 4 a realtime effect sits on a track and processes the audio as it plays and when you export, without touching the recorded waveform. Denoiser plugins from MuseHub work this way, which changes three things:
- No profile. The plugin works out what is noise on its own, so a file that starts mid-sentence, or a conversation with no gaps, is no longer a problem.
- It follows changing noise. A motorbike that passes at 02:14 is treated at 02:14.
- You can keep adjusting. Play, listen, move the amount, compare with the power button. Nothing is committed until you export.
To add one, select the track and press E, or click Effects on the track, to open the realtime effects panel. Click Add effect and choose the plugin; plugins are grouped by format and then by maker, such as VST3 ▸ Viator DSP. The plugin joins the track’s stack with its own power button.
Audacity 4 loads VST3 plugins on every system, Audio Units on macOS and LV2 on Linux, and no longer loads VST2. All three plugins below come as VST3 and AU. How to use effects and plugins in Audacity covers installing through MuseHub and the validation step that makes a new plugin appear.
Viator Voice Denoiser by Viator DSP is free and made for voice, so it is the one to try first. It has a single amount control and does the mid-sentence and changing-noise jobs the built-in effect cannot. In the Add effect list it appears as voice-denoiser under Viator DSP.
Soap Voice Cleaner by Soap Audio is a paid all-in-one plugin for spoken voice, not a denoiser. Its three controls and presets for common microphones target intelligibility, dynamics and harsh resonances. Put it after the denoiser when you clean the same voice every week and want one plugin for the rest of the chain.
Denoiser by Tape It is paid. A machine-learning model detects the noise, a conventional expander does the reduction, and it adapts as the noise changes. It makes sense for regular, demanding cleanup; for an occasional podcast episode the free option gets you most of the way. The best Audacity plugins lists more, with a format column for each.
The AI route: OpenVINO Noise Suppression (Audacity 3 only)
Audacity also has a free AI noise suppressor. It comes with the OpenVINO AI Tools plugin, published by Muse Group and installed through MuseHub. It does not run in Audacity 4 yet; it needs Audacity 3.7.4 or a later 3.x release, which MuseHub carries as Audacity 3. The two versions install side by side.
In Audacity 3 it sits at Effect ▸ OpenVINO AI Effects ▸ OpenVINO Noise Suppression, with a choice of device and model; its Preview button stays greyed out, so apply it to a short stretch and undo with Ctrl+Z if it goes too far. Two things set it apart from the built-in effect:
It needs no noise profile. The model already knows what speech sounds like, so it separates voice from background without a silent moment to sample.
It is optimized for spoken word. That helps on podcasts, interviews and voiceover; on music it can do strange things to sustained notes and cymbals. For a vinyl rip or an instrumental recording, the built-in Noise reduction effect is usually the better choice.
It runs entirely on your own computer, with no uploads and no subscription. On Audacity 4, a realtime denoiser from the section above gives the same no-profile result today.
The methods compared
| Method | Best for | Needs a noise profile? | How it runs | Audacity version | Cost |
|---|---|---|---|---|---|
| Built-in Noise reduction | Steady hiss, hum, fan noise; music as well as speech | Yes | One-off, changes the waveform | 4 (and 3) | Free |
| Viator Voice Denoiser | Voice with changing noise or no clean gap | No | Realtime, on the track | 4 | Free |
| Soap Voice Cleaner | Polishing the voice after denoising; not a denoiser itself | No | Realtime, on the track | 4 | Paid |
| Denoiser (Tape It) | Regular, demanding cleanup work | No | Realtime, on the track | 4 | Paid |
| OpenVINO AI Noise Suppression | Speech, if you still run Audacity 3 | No | One-off, changes the waveform | 3.7.4+ only | Free |
Noise reduction is not a noise gate
The two get confused, and Audacity 4 keeps them in the same submenu.
Noise reduction subtracts a noise fingerprint from the whole recording, including underneath the speech.
A noise gate turns the audio down whenever it drops below a threshold. The noise vanishes between words and is still there underneath them, which can sound worse, because the background now switches on and off with every sentence.
Audacity 4’s gate is at Effect ▸ Noise removal and repair ▸ Noise gate. Its analysis function measures a stretch of pure background and reports the level, so you can set the threshold just above it. The dialog opens with Select Function on Gate, Gate threshold at −40 dB and Level reduction at −24 dB, so the gate turns the background down rather than to silence. The Noise gate page of the manual recommends gentle reduction because it is less noticeable than hard switching.
Gates suit a noisy multi-microphone setup where inactive microphones should go silent. For that job a realtime gate such as the free Renegate from Auburn Sounds sits on each track and keeps working through the export. For cleaning up a single voice, reduction is the tool.
FAQ
Next steps
If Audacity itself is new to you, how to use Audacity starts from the installer. Once the noise is gone, make the recording louder.
Noise is one step of a podcast edit. How to edit a podcast in Audacity puts it in order with the cutting, leveling and export. Mixing your podcast covers levels and balance, and the best podcasting plugins covers the processing that follows.
AI audio editing in Audacity covers the rest of the OpenVINO plugin, and recording a turntable into Audacity covers surface noise on records. For what goes on top of a clean voice, see podcast sound effects; to compare editors, the best free audio editing software.
Get Audacity, the free Viator Voice Denoiser and the rest of the plugin catalog in one place — download MuseHub free.
