Filtering out background noise

Hello, I just started using audacity to try as best as possible to separate voice audio from background noise such as vibration, road noise, and background music. This was audio from a voice recorder. Since I’m brand new to this, I could use some help with which filters to use. Thank you in advance for your help!

Let’s start with the BAD NEWS, that if the noise is bad there’s not much you can do and “the cure can be worse than the disease”. Pros still record in soundproof studios with good equipment and good mic placement. On-location movie dialog is re-recorded in the studio.

You can try the [u]Noise Reduction Effect[/u]. (But again, noise reduction works best when you have a constant low-level background noise… It works best when you don’t REALLY need it.)

You can also experiment with [u]Equalization[/u]. I assume this is a voice recording, so you can reduce the lowest frequencies below around 200Hz and below without much effect on the voice. And if there are very-high frequency noises, you can reduce everything above around 5000Hz. (The low-frequencies are on the left-side of the equalizer and the high-frequencies are on the right, and for experimenting I like to use the Equalizer in the “Graphic EQ” mode with the sliders.)

Thanks for your reply. Yes it is a voice recording, trying to filter out background noise as best as I can. So trial and error sounds like what’s in store for me. I’ve already tried a few of the suggested ones, which work ok. One issue I have encountered is when I try a filter and it doesn’t work, I can’t figure out how to reverse it? So I usual restart the project from scratch. Any suggestion on that?

“Ctrl + Z” to undo the last command.

It is recommended you make a WAV (Microsoft) copy of the original work and save that somewhere safe. Once you apply filters or effects and close Audacity, there is no UNDO no matter how hard you press Control-Z. That’s the end of the world. Audacity Projects won’t help you, either. They don’t preserve UNDO.

There are possible solutions to some of those problems, but a serious problem is leaving the radio on. That’s one of the guaranteed ways to kill your show. #4.

The Four Horsemen of Audio Recording (reliable, time-tested ways to kill your show)
– 1. Echoes and room reverberation (Don’t record the show in your mum’s kitchen.)
– 2. Overload and Clipping (Sound that’s recorded too loud is permanently trashed.)
– 3. Compression Damage (Never do production in MP3.)
– 4. Background Sound (Don’t leave the TV on in the next room.)

I’m a great fan of using portable sound recorders, but you picked a sucky place to do it.

It is possible to build the environment into your voice recording. Do a stand-upper at the harbor and put boat noises in the background. But voice competition is forbidden. Then the harbormaster does an announcement on the loudspeaker system, you have to stop talking. You can’t both be there at once.

What was the recorder? I have a couple of the Olympus units, a no-name USB recorder, a Zoom H2 and an iPod.

The Zoom works very well, but that’s no challenge. I found a recording app (not voice) for the iPod which works far better than you think.


Thanks for your time. I’m not recording anything in a controlled environment. I am monitoring using a covert voice recorder in a car. So just trying to filter out radio, road noise, and vibrations as best as possible. Thanks.

Oh. Surveillance. We don’t do that. Whatever corrections you can derive on your own is what’s available.


Oh, I called the manufacturer of the recorder and they are the ones that recommended Audacity to me.

they are the ones that recommended Audacity to me.

That’s less benign than you think. Because of Audacity’s open source cost ($0), a project can fail and nobody is out any money.

We still don’t do surveillance.


You can use Audacity for whatever you like, but on this forum over the years. we have received support requests for all manner of “surveillance” jobs, many of which were immoral and possibly illegal. The forum helpers don’t want to be in a position of making moral or legal judgements, and also, such jobs usually come down to highly specialised and technical questions about audio forensics, so we decided on a blanket rule that we don’t provide “audio forensics” advice. Our recommendation is to seek professional advice from an audio forensics expert.

Normally, posts asking for audio forensic advice are rejected with an explanatory note before they appear on the forum, but your post slipped through because it was not obvious that was what you were asking about. Nevertheless, I support the decision of the (volunteer) forum helpers to “not do audio forensics questions”.

Thank you for explaining that to me. For what it’s worth it’s nothing immoral, at least not from my end. Thanks.

Nevertheless, digging specific sounds out of a bed of other sounds is difficult and specialised work, quite unrelated to what is technically referred to as “Noise Reduction”.
One approach that is taken by audio forensics experts (though probably with much more specialised and expensive software), is called “spectral editing”. Audacity has some rudimentary spectral editing features that you could try (though there may not be much practical benefit, you may find it interesting). See: