Cleaning up background noise question...

Hello all,

Fairly new to Audacity but I am familiar with the basic functions and uses.

My wife recently used her iPhone video to record a conversation between her and her boss. I was able to reduce the white noise with the “Noise Removal” effect which helped some to improve the quality. My questions is this: There are several yelling children in the background - would it be possible to isolate their voices and remove them? As far as I can tell this track is mono (I used VLC to extract the audio from the .mov file and saved it as a .mp3) so there are no channels for me to drop out, everything is all together…

Any help would be greatly appreciated.


Not in the way you think, no. The only way to get rid of selected voices is if they appear by themselves. That is, person A stops talking briefly and person B starts talking, then you can drag-select the timeline for one of the two voices and silence it with Command-L. If they’re both talking at the same time, you’re dead. That’s borderline forensics/CSI territory.

There may be something you can do with a fancy application of the noise removal tool, but that again depends on you being able to capture one of the offending voices by itself to “train” the tool, and the results are never pretty and many times not even effective.

You have a version of number four.

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 mom’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.)


A common problem with posts like this is the absence of goal. What’s the goal, I mean the real goal?

You also inadvertently violated item number three. Every time you compress audio it gets rattier and harder to process. You went through two compression steps, the original video and MP3 – each contributed sound damage. Koz

Thanks Koz,

Main goal is just trying to make the focal conversation audible… But as it were/are chances are slim. Audacity does accept .mov files - would I have better luck with the original file rather than extracting the audio? All in all this sounds like a dead end but I don’t mind trying just for the experience.

Thanks for the information Koz.

To answer your question the only goal here is to try to clean the clip up enough to be able to hear the focal conversation. As it is now there is too much other noise to make out any content.

That said; I noticed that Audacity would open a .mov file. Would I have anything to gain by using that file directly instead of the compressed .mp3 file?
Also I noticed that if you zoom into the wave length close enough you can actually edit the “range” (?) with the draw tool. Is there anything to gain by messing with that?

Thanks again.

Sorry for the double post… Rookie move, I forgot to wait for approval.

We need to make sure you’re not trying to sell us new kitchen cabinets. That goes away after a while.

clean the clip up enough to be able to hear the focal conversation.

So we’re in forensics territory. We don’t do so good there. Actually most programs don’t, except the ones on “CSI” and “New Tricks.” Script writers tend to be really good at this.

To specifically answer you, yes, with the FFMpeg software installed, you can skip one compression step and its attendant damage by importing the video directly. But don’t call the newspapers yet. Our fuzzy rule is if you can’t understand the voices before the software, you won’t after, either.

You won’t gain anything by messing with the blue waves in detail. Barely audible sound doesn’t produce particularly significant waves. The problem is one of “keys.” The Vocal Removal Tool works by keying in on sound that is exactly the same left and right – usually the lead singer. I could program that and I’m not a programmer.

Noise Removal keys in on the profile that you created for it in the first pass of the tool – you give it a taste of the interference. It then tries to delete the profile sounds from the show – usually low level hum, buzz, or air conditioner noises.

Separating multiple voices from each other doesn’t give you any keys. Electrically, voices are remarkably similar and it’s like deleting a specific amount of chocolate from a cake.


If we could clean up sound, we wouldn’t still be doing this:

Those microphones are close to the speaker for a reason.


Koz, Thanks again. You’ve probably saved me hours of pointless fiddling with this clip. I’ll get back to my CNC machine where I know that the heck I’m doing. No really, I’ll inform my wife that unless she starts seeing Horatio Caine on the side she is out of luck.


I haven’t seen CSI Miami in a very long time. It used to be my favorite and then they scrambled some of the actors and lost me.