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The How-To Geek Guide to Audio Editing: Basic Noise Removal

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Laying down some vocals?  Starting your own podcast?  Here’s how to remove noise from a messy audio track in Audacity quickly and easily.

This is the second part in our series covering how to edit audio and create music using your PC. Be sure to check out the first part in the series, where we covered the basics of using Audacity, and then check out how to add MP3 format support as well.

Removing Noise in Audacity

Open up your file in Audacity, and find the largest contiguous silence in the track.  What we’re going to do is find a baseline for the “noise” so that Audacity knows what to look for.  You can play through the audio to find some silence, but once you do, hit the “Stop” button, and highlight the silence by left-clicking and dragging.  It’s just like selecting anything else, really.

01-highlight silent area

Next, go to Effect > Noise Removal.

02-noise removal

You’ll see a window pop up like so:

03-get noise profile

Click on the “Get Noise Profile” button and the window will go away.  Now, select the portion of the track you want to remove noise from.  For me, it was everything, so I hit CTRL+A to select all. 

04-select all

Again, go to Effect > Noise Removal.  By moving the slider for noise reduction, you’re telling Audacity how much to filter out.  Higher values will be more aggressive removal, while lower values will be more subtle.

04-move slider

You can click the “Preview” button if you want to listen to a small snippet of your track.  You can leave the other two sliders alone, and hit OK when you’re done.

Give your track a listen, and if you need to tweak, you can always hit CTRL+Z to undo and start over.  If you reduce by too much, the track will noticeably sound a little off.  It’s best to be more subtle, that way the audio still sounds natural.

The changes may not be so obvious on the waveform, so I zoomed in to illustrate the smoothing of the waveform.  Here’s what it looks like before and after the effect is processed:

before_after

Enjoy your noise-free audio.

Yatri Trivedi is a monk-like geek. When he's not overdosing on meditation and geek news of all kinds, he's hacking and tweaking something, often while mumbling in 4 or 5 other languages.

  • Published 01/13/11

Comments (9)

  1. Hatryst

    Just in time :) I’ll try it now on a recording i just did…

  2. beriukay

    Interesting. I’ve always gotten the noise profile by selecting the entire track. I would predict that this way would be much faster to analyze, especially with bigger files, than the way I’ve been doing it. I’m really curious to see how the sound quality differs between these two methods.

  3. Chris

    The reasoning behind selecting a silent portion is so that the noise removal algorithm can get the characteristics of what we consider “noise” and then remove that from both the sections we want to be silence and the sections where there is the sound we originally wished to record.
    Profiling the entire track defeats the purpose. You aren’t giving the plugin any information about what is noise and what is content.

    Some bluetooth headsets use two microphones, one pointing away from the user and one pointing toward. The processor in the headset can then better distinguish what is background noise and subtract it from what the primary mic picks up. Profiling the “silent” parts of the recording lets us act like that second microphone.

  4. John

    You’ll also not want to reduce it by too much. It can distort the good audio in some cases if it is over applied.

  5. JayMo

    Very nice. Thanks again! I’m looking forward to the rest you’ll be posting on this. :)

  6. lilruchira

    Thanks

  7. Jasmin

    thank you…

  8. PugLives

    I’m an 80′s kid, so I’m only a kid at heart – but I’m giddy after reading this! As a family guy (and gals) we can now edit audio tracks from our home recordings so we can here inclement George or little Suzi’s recital….you know without turning it up so much you have that huummmm. I’m sure there will be more to learn for a home movie clip and all, but now I know I can!…….but the kid in me will just like to say/brag “Let me clean up that audio, see what can find here…” like on CSI Miami!

  9. PugLives

    Oops, see that should have been “uncle” George….this kid at heart reads How To Geek on his Droid Incredible(my first smart phone!…incredible!) while my legs fall asleep on the throne! ….shut up, every guy does it :)

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