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Audacity Noise Reduction Guide (3.7 Manual, 2026)

Reduce steady noise in dialogue while checking that the voice stays intact.

Audacity 3.7 manual workflow

Download printable workflow

Select noise alone, then process the dialogue A shaded noise-only pause at the left is the profile. The speech region at the right is the audio to clean. This is a schematic, not a measured waveform.

Selection diagram, not recorded audio.

  1. Profile. Select noise alone. Open Noise Reduction; choose Get Noise Profile.
  2. Preview. Select the dialogue. Reopen the effect. Adjust one control at a time.
  3. Check. Listen to Residue for lost words. Switch to Reduce before OK.
Which repair fits this noise?
  • Steady hiss under speech: Noise Reduction.
  • Narrow hum or whistle: Notch Filter first.
  • Noise in quiet gaps: Noise Gate.
  • Traffic bursts or clicks: profile-based reduction may not fit.

Last updated October 23, 2026.

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Audacity noise reduction works best on a steady background sound, such as fan hiss, when the voice is much louder. It needs a sample of that noise on its own. Start with the noise-only profile, then listen to both the kept sound and the removed sound before you apply the effect.

This workflow follows the Audacity 3.7 reference manual. Use Noise Reduction for steady noise across speech, Notch Filter for a narrow hum or whistle, and Noise Gate for noise in quiet gaps. Save the original first. Aim for speech that sounds natural, even if a little room noise stays. The listening checks matter more than a preset.

Audacity noise reduction: choose the right repair

The Audacity manual labels this reference as version 3.7. This is a documentation-based guide, not a claim that 3.7 is the newest release. Names and menu positions may differ in another version. Check the manual linked from your own copy of Audacity when a control does not match.

  • Steady hiss or fan noise: use Noise Reduction. It learns the sound from a noise-only selection.
  • A narrow hum or whistle: try Notch Filter first. It cuts a small frequency range. A frequency is the rate at which a sound wave repeats.
  • Noise between words: Noise Gate lowers sound that falls below a level you set. It does not remove hiss that sits under a loud voice.
  • Traffic, crowd bursts or isolated clicks: do not expect a steady-noise profile to solve these. The manual says Noise Reduction is poorly suited to noise that changes or to single clicks and pops.

For example, a room fan through an interview may fit Noise Reduction. A passing car that drowns out a word does not provide the same kind of stable noise. Listen to the clip before choosing a repair. A stronger setting cannot restore speech that the noise has masked.

Select a noise-only profile in Audacity

Choose a patch from the same recording that contains the unwanted sound with no voice or music. The patch teaches the effect what to reduce. Do not select a whole spoken sentence for this step. That would teach the profile about sound you want to keep.

  1. Keep an unchanged copy of the source recording. Save the working project separately.
  2. Find a pause with the same background noise as the dialogue. Listen to the selection on its own.
  3. Drag across that noise-only patch in the waveform, the picture of sound level over time.
  4. Open Effect > Noise Removal and Repair > Noise Reduction.
  5. Choose Get Noise Profile. Then select the dialogue region you want to clean and reopen the effect.

The Noise Reduction manual requires at least 2,048 samples, about 0.05 seconds at 44,100 Hz. It prefers a longer sample. These are the manual's limits, not a suggested length for every recording. Use a real, steady pause when you have one. Copying a tiny noise fragment over and over does not add useful information.

Check the start and end of the selection for a breath, a mouth noise or a faint word. If the only pause has a different sound from the rest of the take, the profile may not fit. When the noise changes between parts of a recording, the manual advises separate profiles and passes for those parts.

The profile is lost when you close Audacity. Capture it again in a later session. The profile and the audio being processed must also have the same sample rate. The manual says Audacity blocks a mismatch. A sample rate is the number of audio samples per second; do not change it just to bypass that check.

Set Audacity noise reduction controls

Set the controls while the region to clean is selected. The values below come from the 3.7 Noise Reduction manual. They explain the controls; they are not a promise that the listed defaults will suit your voice. Preview a phrase with soft words as well as a noisy pause.

Noise Reduction (dB): how far the noise is lowered

This control sets how much the effect turns down the noise it finds. The manual lists a default of 6 dB. Use the least reduction that makes the clip useful. Raising it can leave less hiss, but can also harm the voice. A decibel, or dB, expresses a level difference.

If words become thin or dull, back off and compare again. Do not judge only the gaps. Noise that remains under speech may matter less than a voice that sounds processed. Keep the listening volume steady so the quieter background does not hide damage to the words.

Sensitivity: how much sound counts as noise

Sensitivity controls how readily Audacity treats sound as noise. The documented range is 0 to 24, with 0 off and a default of 6.00. A higher value can catch more noise, but may take parts of the voice too. A low value can leave short, strange tones behind.

Use the lowest value that removes enough noise without those tones. If lowering it saves a soft word but produces ringing, do not keep raising the reduction to compensate. Recheck the profile, compare a gentler pass and use the Residue check below to hear what is being lost.

Frequency Smoothing (bands): spread the reduction

Smoothing spreads the change across nearby frequency bands. A band is a small slice of the sound's frequency range. The manual lists a default of 6 bands. It suggests trying 0 when the wanted sound is strong and broad and the noise is light. Smoothing can make the result less clear.

If odd tones remain after you have set Sensitivity as high as you can without losing wanted sound, the manual suggests 1 to 6 bands. Preview the change rather than assuming more is better. This control can make artifacts less harsh; it does not prove that the speech is intact.

Preview Reduce and Residue before applying

Reduce lets you hear the cleaned result. Residue lets you hear what would be removed. Use both. A quiet result alone does not show that the effect has kept all the speech. The manual's Residue advice is to listen for recognizable parts of the wanted sound.

  1. Choose Reduce, then Preview. Listen for clear words, natural breaths and a steady background.
  2. Choose Residue, then Preview again. Hiss in this check is expected. Recognizable words or music are a sign that wanted sound is being removed.
  3. If you hear the voice in Residue, lower Sensitivity or Noise Reduction and preview again.
  4. Switch back to Reduce before you choose OK. Otherwise you will apply the removed-sound output instead of the cleaned result.
  5. Play the processed section in the scene. Compare with the source, including the quiet ends of words and pauses.

Preview a section that includes both quiet and loud speech. A setting that seems fine on a loud phrase can take away a soft ending. If the effect helps the pause but harms the words, undo it. Some noise is often a better trade than damaged dialogue.

Fix watery, metallic or ringing artifacts

Artifacts are new sounds caused by processing. The Audacity manual describes brief tones that can sound like bells or birds. They may arise when the profile does not represent the noise, or when Sensitivity is too low. An aggressive pass may also remove wanted sound. Check which problem you hear before changing a control.

  • The voice is in Residue: lower Sensitivity or the reduction amount. Recheck both outputs.
  • Short ringing tones remain: check that the profile matches the take. Then follow the manual's Sensitivity and smoothing advice above.
  • The noise changes across the clip: treat each distinct section with its own representative profile.
  • The result sounds worse than the source: undo it. Compare a lighter pass rather than stacking more repair on top.

Change one control at a time. That makes it easier to hear the cause of a change. The manual warns that very loud noise, noise close to the speech in level, or noise with much the same frequencies may prevent a useful result.

The manual also flags a bug when this effect is used with an amplitude envelope: the envelope may be removed. An envelope is a drawn level change. Keep an unchanged project copy and check those level changes after processing. Read the manual's current warning before applying the effect to a time-stretched clip, too.

Use Notch Filter and Noise Gate for their own jobs

For hum, Notch Filter is under Effect > EQ and Filters. Find the tone with Analyze > Plot Spectrum, then set the notch frequency to match it. Do not pick a mains frequency just from where you live; use the recorded noise as your check.

The manual lists 60 Hz as the notch's default frequency and 1 as its default Q factor. A higher Q makes the cut narrower; a lower Q makes it wider. Its hum example uses 50 or 60 Hz and suggests Q 2 to 10. Those are examples, not a preset for every clip.

Repeated hum tones at higher frequencies may need separate cuts. The manual places notch filtering before Noise Reduction.

Noise Gate is under Effect > Noise Removal and Repair. Use its Analyze Noise Level function on a selection that begins with noise only. The manual says analysis reads the first half second. Use the suggested threshold as a starting point, then preview soft speech.

A threshold is the level below which the gate turns sound down. Set it too high and soft words can fall below it. Attack controls how the gate opens, Hold keeps it open after sound drops, and Decay controls how it closes. Use those controls by ear. The manual warns that too much level reduction can make the background pump as the gate opens and shuts.

Export cleaned dialogue for your edit

Save the working project, then use File > Export Audio to make an audio file. The Export Audio dialog manual describes the choice of whole project or current selection, file format and output settings. Saving a project is separate from exporting sound for your video editor.

Check the export range so you do not send only the noise-profile pause. Choose the format, channels and sample rate your edit requires. Keep the original recording and use a new filename for the cleaned file. Import that export into the edit and listen across the cut, where a sudden change in room tone may stand out.

For the next shoot, our audio recording devices guide helps with choosing a recording setup. Fixing the recording path comes before relying on repair to rescue each take.

Audacity noise reduction FAQ

What if there is no noise-only pause?

Do not use spoken words as the profile. Look elsewhere in the same recording for the same steady noise with no wanted sound. If none exists, this profile-based workflow may not fit the clip. A room recording from a different setup is not proof of the noise under this voice.

Can I keep applying Noise Reduction?

Each pass can change the wanted sound as well as the noise. Compare with the untouched recording before adding another pass. For distinct kinds of noise, the manual describes separate profiles. That is different from repeatedly applying an aggressive setting to the same steady hiss until every gap is silent.

Why can I hear words in Residue?

Residue is the sound the effect plans to remove. Recognizable words mean the chosen settings may be taking speech. Lower Sensitivity or Noise Reduction, preview again, then return to Reduce. Check the soft parts of the take before applying. A cleaner pause is not worth losing the line.

Will Noise Gate remove hiss under speech?

A gate acts on level. When the voice is above the threshold, the gate opens and the background can pass with it. It is useful for gaps, but it is not the same as learning a noise profile. Use a gentle gate only when the change between open and closed sounds natural.

Audacity noise reduction verdict

Use a real noise-only profile, keep the pass light and check Residue for lost speech. Audacity noise reduction has done its job when the dialogue is easier to use and still sounds like the source. A trace of room noise can be the better result.

Source notes: this guide paraphrases the linked Audacity manual, licensed CC BY 3.0. Audacity's authors do not endorse this site. The diagram and printable workflow are original editorial aids; they do not show measured audio or promise a particular noise-reduction result.

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