Audacity Forum

I am using Audacity 1.2 to remove wind/traffic noise from recordings of bird songs for scientific research. I have been very successful using the 'slider' in version 1.2, however, to report my findings I will need to quantify my noise reduction procedure - "2 clicks on the slider" just won't do. Can anyone explain the actually modifications that each step on the slider is making to the noise removal threshold?

I also tried this procedure on the 1.3 Beta version, but had much less success unmasking bird songs from background noise.

Thanks for your help!

That's not good news. Typically, the noise reduction in 1.3.12 is the only one that works -- and it has clearly marked values in the settings.

We had a couple of posters early on that claimed they got much better noise removal in 1.2 than in the newer version. I was never able to get 1.2 to do anything useful at all. They (and you) may have a particular "noise" that lends itself to the earlier version. That's rare.

But as you found out, Noise Removal in 1.2 is, let's say, basic. It's also not being worked on by anybody and likely to stay that way forever. It's like asking for an operating patch to Windows 98.

It's actually worse than you think. Unless you email a profile to somebody trying to replicate your results, they won't be able to. The initial sample or "Profile" is of paramount importance to the success of the tool. And it doesn't have any controls at all.

Koz

Thanks for your response! Your are right about the profile varying. In fact, it will vary for each track that I am analyzing because the ambient noise that needs to be removed is different for each track. But if I could state that I made a profile of ambient noise for each track, and then removed noise that did not exceed a XXdB threshold beyond that of the noise profile, I think that would be sufficient. It seems that this must be written in the code for 1.2 somewhere, but I'm probably naive on this. I will continue to try and work it out with 1.3, but any further guidance would be great. Thanks.

For some types of noise/signal combinations you can get better results in Audacity 1.3 if you amplify the noise by around 6 to 10 dB before you make your noise profile.

I can give you fuzzy instructions for the Noise Reduction in 1.3

Amount of reduction varies from no correction at all on the left to total overkill on the right. Gentle correction hovers around maybe 12dB or 18dB.

Smoothing is the magic one. Too far to the left gives you gargly, bubbly martians. Too far to the right gives you noise tails following each spoken word around like a puppy dog. I've used values from 150 to 500.

I've never done much with Delay, so I don't know. Use the default.

This tool is much more of a juggling act than the old one was. The old one worked or it didn't.

Both noise reductions can cause damage to the show, however slight. If the song is louder than the background wind, you might be well served with the noise gate tools.

http://forum.audacityteam.org/download/file.php?id=1272

Koz