How to Remove Background Noise from Audio in Audacity: The Complete Guide

If you‘ve ever recorded audio, whether it‘s a podcast, voiceover, or musical performance, you know that annoying background noise can ruin an otherwise great recording. Fans whirring, air conditioning humming, or even the buzz of electrical interference can distract listeners from your content.

Luckily, the free audio editing program Audacity provides several tools to help reduce or eliminate unwanted background noise. As a longtime Audacity user, I‘ll walk you through how to remove background noise in Audacity step-by-step. I‘ll explain the various settings to achieve the best results and also share some advanced techniques and alternative options. Let‘s dive in!

Using the Noise Reduction Effect

Audacity‘s built-in Noise Reduction effect is the first stop for removing background noise. Here‘s how to use it:

1. Always work on a copy of your original audio file. Audacity‘s editing is destructive, meaning you can‘t undo it once you‘ve saved the file.
2. Find a section of your audio that contains only the noise you want to remove (no talking or other sounds). It can be short, but the longer the better. Select this noise sample.
3. Open the Noise Reduction effect from the Effect menu. Click the "Get Noise Profile" button. Audacity has now learned what the offending noise sounds like.
4. Select all of the audio you want to remove noise from. If it‘s a lengthy recording, you may want to process it in smaller batches.
5. Open the Noise Reduction effect again. Here you‘ll see three settings to adjust:

• Noise reduction (dB): How much noise to reduce in decibels. 0-12 dB is a good range.
• Sensitivity: How much sound should be considered noise vs. desired audio. The higher the number (max 24), the more it will remove (but it may also remove some audio you want to keep). Start low around 3-6.
• Frequency smoothing (bands): Adjusts how much the effect will remove noise in neighboring frequencies. Start at 0 to preserve the most audio quality.

6. Click the "Preview" button to hear what your audio will sound like with noise removed using the current settings. Make sure the "Residue" option is selected to preview what will be removed. If it‘s removing too much of the good audio, turn down the Noise reduction or Sensitivity. If there‘s still too much noise, turn them up gradually. Experiment until you get the best balance.
7. When you‘re happy with the settings, click "OK" to apply the effect to the selected audio.

The Noise Reduction effect works best when the background noise is relatively constant throughout the recording, like an air conditioner hum or white noise. It‘s not as effective for sudden noises like coughs, sneezes, or cars driving by. It will also struggle if the noise is very similar in frequency to the desired audio (like a deep male voice trying to talk over the low rumble of a truck engine).

Keep in mind that no noise reduction is perfect – removing noise will almost always degrade the overall sound quality to some degree. The key is finding the right balance.

Using the Notch Filter Effect

For removing constant tones or hums, like a 60Hz electrical buzz, Audacity‘s Notch Filter effect may give you better results than Noise Reduction. A notch filter removes a very narrow band of frequencies. Here‘s how to use it:

1. Select a section of your audio that contains the tone or hum you want to remove.
2. Plot the frequency spectrum of that audio by clicking "Analyze > Plot Spectrum." You‘ll see a graph showing the volume of different frequencies present in the selected audio.
3. Look for any tall, narrow spikes that don‘t seem to match the rest of the graph. Hover your mouse over the spikes and look at the frequency (in Hz) that appears in the lower left corner. That‘s likely the fundamental frequency of your noise.
4. Close the spectrum plot and select all the audio you want to remove the noise from.
5. Open the "Effect > Notch Filter" tool. Enter the frequency you found in step 3. The Q setting adjusts the width of the frequency band that gets removed – a higher number means a narrower band (which removes less overall sound). Start with the default of 1.0.
6. Click "Preview" to hear the effect, then click "OK" to apply it if you‘re satisfied. Check the spectrum again to see if the spike is gone.

Notch Filter is great for constant tones but not effective for wider-band noise like tape hiss or crowd noise. It‘s most useful when you can clearly identify the noise in the frequency spectrum.

Click and Pop Removal

For removing occasional clicks, pops, or crackles, try Audacity‘s Click Removal effect under the Effect menu. Just select the audio around each click and apply the default settings. You may also have luck with the "Repair" effect for individual pops.

For more intense crackle or record static, try the Decrackler effect in the same menu area. Experiment with the Amount and Frequency Bandwidth settings to reduce as much crackle as possible without losing too much high frequency sound.

Tips for Best Results

• Always use the lowest amount of noise reduction that still sounds acceptable. Over-doing it will make your audio sound hollow, muffled, or robotic.
• If your recording has a lot of noise, consider applying Noise Reduction in several small doses rather than all at once. Select a section, use gentler settings, then repeat on other sections if needed. This can sometimes sound more natural than one heavy-handed pass.
• Does your recording have noise in a frequency range far away from the frequencies of the desired audio (like a high-pitched whistle and a low male voice)? Use EQ effects like the High Pass and Low Pass filters to cut those frequencies out entirely before using Noise Reduction on what‘s left.
• Recording a noisy old tape or record? Try the Equalization effect‘s "RIAA" curve preset to reduce high frequency hiss and low frequency rumble.
• Noise is usually quieter between spoken words or musical phrases. But if you try to remove it, the noise level will suddenly drop out every time the main audio stops, which sounds unnatural. Use the "Compress dynamics" Limiter effect afterwards to smooth this out.
• If you have a recording with noise that fades up or down over time (like a fan that starts mid-recording), you could try automating the Noise Reduction settings to match. Audacity doesn‘t have a way to do this, so you‘d have to split the track into multiple sections and use different settings on each.
• Remember, the best solution is to prevent unwanted noise while recording. Use a quality microphone, record in a quiet environment, keep the mic away from noise sources, and capture the cleanest signal you can. It‘s always better to avoid noise in the first place than to try to remove it later!

When to Use Dedicated Noise Reduction Software

While Audacity‘s noise removal tools are quite capable for a free program, there are times you may want to use a professional audio editor or dedicated noise reduction software. Professional tools like iZotope RX, Adobe Audition, and Waves plugins have more advanced algorithms for identifying and removing noise, especially in tricky cases like dialogue recorded in noisy environments.

Consider upgrading to one of these tools if you deal with noise removal regularly and need the absolute highest quality results. They can better preserve voice frequencies while removing more background noise. Many also have intelligent "learning" modes that can adapt to changing noise over time.

However, for most podcasters, audiobook narrators, and home studio musicians, Audacity‘s built-in tools are a great place to start. With practice and careful adjustments, you can rescue most recordings from distracting background noise.

Frequently Asked Questions

Can I remove background music from a voiceover recording?
This is very difficult to do in postproduction. Audacity‘s Vocal Reduction and Isolation effect can remove some background music from a voice recording, but the voice quality will suffer. It‘s much better to record the voice and music separately if possible.

Can I remove just one person‘s voice from a recording of multiple people talking?
Generally no, it‘s nearly impossible to completely isolate one voice in a recording of multiple voices. The frequencies of human voices are too similar. A noise reduction tool can‘t tell them apart like it can a voice from a low hum.

How can I remove a specific recurring sound, like a dog barking or a phone ringing?
If the unwanted sound has a specific frequency peak you can locate in the spectrum analysis, you can try to reduce it with the Notch Filter effect. Otherwise, your best bet is to delete those individual sounds with the Selection tool and use Generate > Silence to fill in the gaps.

Should I use noise reduction on every recording?
No – only if the recording actually has noticeable noise issues. If your audio is clean to begin with, running it through noise reduction can only hurt the sound quality, not help it. Noise reduction is a "damage control" tool for imperfect recordings, not something you need to do to every file.

I hope this guide helps you clean up noisy recordings and salvage audio you thought might be unusable. Audacity‘s noise reduction tools are surprisingly powerful for a free program. While it may take some trial and error to get the best results, it‘s a skill well worth practicing for anyone working with audio.

Do you have any other tips for removing background noise in Audacity? What‘s the trickiest noise problem you‘ve had to tackle? Let me know in the comments!