How to Remove Background Noise in Audacity
Scope, up front: this guide cleans a recording — a file that already exists. Noise happening live is a different problem entirely; everything below happens after the fact.
Select two to five seconds of pure noise, open Effect → Noise Removal and Repair → Noise Reduction, and grab a fingerprint with Get Noise Profile. Then select the whole track, open the same effect again, and apply it — start at 12 dB reduction, sensitivity 6.00, frequency smoothing 3, and adjust by ear. The whole job takes about five minutes once you've done it twice.
Verified against Audacity 3.7.8 (current since late Jun 2026) on Jul 29, 2026 · works on WAV, MP3, FLAC, OGG — anything Audacity opens · Windows, macOS, Linux.
Placeholder players — the real clips drop in at QA (see deploy notes for the file slots).
Step 1 — Find and sample the noise
- Open your file in Audacity (File → Open, or just drag it in).
- Find 2–5 seconds of noise only — the gap before you started talking is usually perfect.
- Drag to select that noise-only stretch on the waveform.
- Open Effect → Noise Removal and Repair → Noise Reduction, then hit Get Noise Profile — the dialog closes silently, and that's normal.
Why this works: Audacity builds a fingerprint of the noise from your sample, and later subtracts everything that matches it. That's also why the sample must contain no speech at all — anything in it gets treated as noise.
Step 2 — Apply the reduction
- Select the whole track with Ctrl+A (Cmd+A on a Mac).
- Reopen Effect → Noise Removal and Repair → Noise Reduction.
- Enter the starting values: Noise reduction 12 dB, Sensitivity 6.00, Frequency smoothing 3.
- Press Preview and listen for a few seconds before committing to anything.
- Click OK to apply it to the track.
When it fails: if the noise changes over time — traffic swelling, a voice in the next room — the fingerprint stops matching and the method quietly falls apart. It's built for steady offenders: hiss, hum, fans, air-conditioning.
Step 3 — Check your work, then adjust by ear
- Listen to the quiet passages first — artifacts hide where speech is thin.
- Too much noise left? Run a second gentle pass at 3–6 dB rather than one huge pass.
- Voice gone hollow? Undo with Ctrl+Z and retry with lower reduction or higher smoothing.
- Export with File → Export Audio once it sounds right.
Two gentle passes nearly always beat one aggressive one. Each pass starts from cleaner audio, and you can stop at the exact moment the trade-off tips against you.
The classic Audacity mistake is dragging Noise reduction past 20 dB because 12 "didn't feel like enough." What you get isn't silence — it's the underwater voice: hollow tone, lisping consonants, and a warbling artifact engineers call musical noise. The cause is always the same pairing: too much reduction, too little frequency smoothing. A good pass is one you can't hear working.
Still noisy? Escalate in this order
- Still noisy after two passes? You've likely hit the recording's quality floor — re-record if the noise sits less than 30 dB under your voice.
- A low, steady drone that won't die? That's mains hum, not hiss — it needs a notch filter, not Noise Reduction. See the hum & hiss guide.
- Voices in the background? Profile-based tools can't remove other people talking; an AI separator is the only realistic route.
Quick questions
Does Audacity's noise reduction lower voice quality?
A gentle pass — 10 to 14 dB — is close to transparent on most voices. Quality drops when reduction is stacked too high (the underwater artifact) or when noise sits right on top of speech frequencies. Preview first, work in small passes.
Can Audacity remove noise in real time?
No — Audacity edits files after the fact, which is this site's whole beat. Its Noise Reduction is a two-pass, offline effect by design: recordings in, cleaner recordings out.
Is Audacity really free?
Completely. Open source, no account, no usage caps, no watermark — checked on Jul 29, 2026 against 3.7.8, with Audacity 4 in public beta.