You captured a promising EVP session, but when you play it back, all you hear is hiss, hum, and fan noise burying whatever might be underneath. That’s where Audacity noise reduction comes in, a free, powerful tool that can strip away unwanted background sound and let potential evidence speak for itself. For paranormal investigators, clean audio isn’t optional; it’s the difference between a compelling capture and a file you’ll never use.
Here at Haunt Gears, we test and recommend recording equipment built for fieldwork in dark, unpredictable environments. But even the best EVP recorders pick up noise, HVAC systems, electrical buzz, wind, you name it. Knowing how to process that audio after an investigation matters just as much as the gear you bring with you. Audacity handles this well, and it costs nothing to download, which makes it a staple in most investigators’ toolkits.
This guide walks you through exactly how to use Audacity’s Noise Reduction effect, from grabbing a noise profile to dialing in the best settings for paranormal audio cleanup. Whether you’re working with your first recording or your five-hundredth, you’ll get clear, repeatable steps you can apply to any session.
What Audacity noise reduction does and when to use it
Audacity’s noise reduction tool works by learning what "silence" sounds like in your recording, then subtracting that pattern from the entire track. It uses a two-step process: first, you select a sample of pure noise (no voices, no EVPs, just background sound), and then you tell Audacity to reduce that specific noise signature across the whole file. The result is a cleaner track where quiet captures have a better chance of standing out against whatever background noise remains.
How the noise profile system works
When you feed Audacity a noise sample, the tool builds a spectral fingerprint of that background sound. Think of it as showing the software what to ignore: every frequency that matches your noise profile gets turned down, while frequencies that don’t match stay at their original levels. This is why the quality of your noise sample matters enormously. A two-to-four second clip of clean background noise, recorded before or after your EVP session, gives Audacity the most accurate fingerprint to work from.
The better your noise sample, the more surgical Audacity’s noise reduction becomes. A short, clean sample beats a long, cluttered one every time.
Audacity processes the profile using three main controls: Noise Reduction (dB), Sensitivity, and Frequency Smoothing. Each one affects how aggressively the tool removes noise and how much it blends the processed frequencies with surrounding audio. You adjust these values inside the Effect menu after loading your profile, and small changes in each setting can produce noticeably different results on the same file.
When to use noise reduction (and when not to)
Steady, consistent background sounds are where Audacity noise reduction performs best. HVAC hum, electrical buzz, recorder self-noise, and fan hiss are all strong candidates because they stay relatively constant throughout a recording. If the noise in your file doesn’t shift much from second to second, Audacity can profile it accurately and remove it cleanly without much collateral damage to the audio around it.
You should skip noise reduction, or use it very lightly, when your background noise changes frequently or when the noise and the signal you want to preserve share similar frequencies. Rain, wind gusts, and footsteps shift constantly, and heavy processing on those sounds often damages the material you’re trying to protect. Similarly, if a potential EVP or voice sits in the same frequency range as the hum you’re removing, pushing the reduction too hard will pull that evidence out along with the noise.
Here’s a quick reference for common paranormal recording scenarios:
| Noise Type | Good Candidate? | Notes |
|---|---|---|
| HVAC / air handler hum | Yes | Consistent, easy to profile |
| Electrical buzz (60 Hz) | Yes | Consider Notch Filter first |
| Recorder self-noise / hiss | Yes | Keep Noise Reduction (dB) moderate |
| Wind gusts | No | Too variable to profile cleanly |
| Footsteps / movement | No | Overlaps with EVP frequencies |
| Rain | No | Changes too often throughout the recording |
Step 1. Prep your track and get a noise profile
Before you touch any settings, your recording needs to be imported and your noise sample needs to be located. Open Audacity, go to File > Import > Audio, and load your EVP file. Once the waveform appears, you’re looking for a section where only background noise is present, with no voices, no movement, and no potential captures. Most investigators find this in the first few seconds of a recording, right after they pressed record and before anything happened in the room. That quiet lead-in is your best starting point.
Find and isolate your noise sample
A good noise sample runs two to four seconds long and contains nothing but the consistent background hiss, hum, or buzz you want to remove. Scan your waveform visually: flat, low-amplitude sections are your best candidates. Click and drag to highlight one of these sections, then listen back by pressing the spacebar. If all you hear is steady, unchanging background noise with no dips or spikes, you’ve found a usable profile region.
If your recording has no clean noise-only section, record two to four seconds of room ambiance at the start of your next investigation and import that file separately to pull the profile from.
Follow these steps to capture the noise profile:
- Click and drag to highlight your noise sample in the waveform.
- Go to Effect > Noise Reduction in the top menu.
- Click "Get Noise Profile" inside the dialog box.
- Audacity closes the dialog automatically once it stores the profile.
Select the full track before applying
After Audacity captures the profile, select your entire track by pressing Ctrl+A on Windows or Command+A on Mac. This tells the software to process the whole file rather than just the small section you used for the profile. Skipping this step is the most common error new users make, and it results in only a narrow slice of your audio getting treated while the rest stays buried in noise. With the full track selected, you’re ready to dial in the audacity noise reduction settings in the next step.
Step 2. Choose the best settings for your recording
With your noise profile captured and your full track selected, open Effect > Noise Reduction again. This time the dialog stays open so you can adjust the three sliders before applying anything. Each slider controls a different aspect of how aggressively Audacity strips noise from your audio, and getting the balance right prevents you from damaging the very recordings you’re trying to clean up.
The three sliders and what they control
Noise Reduction (dB) sets how much volume reduction Audacity applies to frequencies that match your noise profile. Higher values cut more noise but also risk pulling out quiet audio that sits near the noise floor, which is exactly where most EVP captures live. Sensitivity controls how broadly Audacity identifies sounds as noise: a higher value flags more frequencies as noise and removes them, while a lower value stays more conservative and protects borderline audio. Frequency Smoothing (bands) blends the processed frequencies with surrounding ones to prevent harsh, unnatural cutouts in the sound.
Treat these three sliders as a system rather than independent controls. Pushing one too far without adjusting the others is the most common cause of that metallic, warbling sound that ruins otherwise clean processed audio.
Recommended starting settings for EVP and paranormal audio
For most paranormal recordings, these starting values give you a solid baseline without over-processing your file. Use the table below as your reference point before you run your first preview:
| Setting | Starting Value | Range to Explore |
|---|---|---|
| Noise Reduction (dB) | 12 | 6 to 18 |
| Sensitivity | 6 | 3 to 9 |
| Frequency Smoothing (bands) | 3 | 1 to 6 |
Start at 12 dB Noise Reduction with Sensitivity at 6 and Frequency Smoothing at 3. These values remove a noticeable amount of steady background hiss without introducing the warbling artifacts that come from more aggressive audacity noise reduction settings. If your recording carries heavy electrical hum rather than hiss, nudge Noise Reduction up to 15 dB and drop Sensitivity to 4 to keep the processing targeted. Always click "Preview" inside the dialog to audition a short section of your audio before committing to the full track.
Step 3. Apply noise reduction and fine-tune the result
Once you’ve previewed the result and you’re satisfied with how it sounds, click OK in the Noise Reduction dialog to apply the effect to your entire track. Audacity processes the full selection and renders the cleaned audio directly in the waveform. Always export a copy of your original file first before you click OK, because applying the effect is permanent once you save and close the project.
Apply the effect and save your work
After clicking OK, your waveform will visibly flatten in the quieter sections where steady noise has been removed. The track won’t look dramatically different at a glance, but the noise floor will drop, and softer material underneath will have more room to stand out. Before you do anything else, go to File > Export > Export as WAV and save a processed version with a distinct file name so you always keep your unedited original intact. Never overwrite your raw recording file.
Always work from a copy of your original file. Once you export a processed version and close the project, you can’t reverse the noise reduction you applied without starting over.
Follow these steps to apply and save cleanly:
- Confirm your full track is still selected using Ctrl+A (Windows) or Command+A (Mac).
- Open Effect > Noise Reduction and click OK.
- Let Audacity finish processing the waveform.
- Go to File > Export > Export as WAV and save the processed file under a new name.
Fine-tune by running a second pass or adjusting settings
If your first pass left too much noise behind, select the full track again and run audacity noise reduction a second time using slightly different values rather than jumping straight to a higher Noise Reduction (dB) setting. Drop Sensitivity by one point and raise Frequency Smoothing to 4 before running another preview. Multiple light passes often produce cleaner results than one aggressive treatment, and they significantly reduce the chance of introducing warble or metallic artifacts into your captures. If the second pass sounds worse, press Ctrl+Z (Windows) or Command+Z (Mac) to undo and try a different combination of values before committing. Keep notes on which settings you tested so you can reproduce your best result on future recordings from the same location or the same recorder.
Fix common problems like warble, hiss, and hum
Even with careful settings, audacity noise reduction sometimes creates new problems rather than solving the ones you started with. The three most common issues investigators run into are warble, leftover hiss, and stubborn low-frequency hum. Each one has a specific cause and a specific fix, so troubleshooting them is straightforward once you know what to look for.
When your audio sounds metallic or warbled
Warble shows up when your Noise Reduction (dB) or Sensitivity settings are too high for the recording you’re processing. Audacity starts removing audio that doesn’t belong to the noise profile, and the result is a hollow, robotic quality that distorts any genuine captures in the track. Press Ctrl+Z (Windows) or Command+Z (Mac) to undo the effect immediately, then reopen the dialog and drop your Noise Reduction value by 3 to 6 dB before running another preview. Raising Frequency Smoothing from 3 to 5 also helps blend the processed frequencies more naturally and reduces the mechanical quality in the output.
If warble keeps appearing even at lower settings, your noise sample may contain audio that overlaps with the material you’re trying to preserve. Try finding a cleaner two-second sample from a different part of the recording.
Persistent hiss after processing
Leftover hiss usually means your Sensitivity setting is too low, so Audacity is flagging fewer frequencies as noise than it should. Select the full track again, reopen the Noise Reduction dialog, and raise Sensitivity by one or two points before running a second preview. If hiss persists after that adjustment, check whether your noise sample was long enough and free of any audio artifacts. A sample that includes even a faint sound teaches Audacity the wrong profile, which limits how effectively it can target the true background noise.
Dealing with electrical hum
A constant 60 Hz hum from electrical sources responds better to Audacity’s Notch Filter than to noise reduction alone. Go to Effect > Filter Curve EQ or use the Notch Filter option, target 60 Hz (and 120 Hz for the harmonic), and apply a narrow, deep cut. Run noise reduction afterward to handle any remaining hiss, and the combination will produce a much cleaner result than either tool produces on its own.
Wrap-up and next steps
You now have a complete, repeatable workflow for audacity noise reduction: capture a clean two-to-four second noise sample, load the profile, start with 12 dB Noise Reduction and Sensitivity at 6, preview before committing, and export a processed copy while keeping your original intact. Multiple light passes beat one aggressive reduction, and the Notch Filter handles stubborn 60 Hz hum before you run noise reduction at all.
Putting cleaner audio to work starts with gear that captures higher-quality recordings from the start. Better hardware means less background noise entering your files, which means less processing time and more reliable evidence to analyze. Browse the full range of professional-grade paranormal investigation equipment at the Haunt Gears shop and find tools built for serious fieldwork, from EVP recorders to EMF meters and thermal cameras, so your next investigation gives you the cleanest raw audio possible before you even open Audacity.
