Hey there. I’m new to all this sound stuff. I usually edit my audio by following a quick tutorial I found on the web. It really helps, but everytime I remove the noise my audio ends up with two parts: one where I really removed the noise, other, where there’s a strange annoying noise on the background. Sometimes this sound just gets between my lines, but others it’s on the background of when I’m speaking. I’m uploading the noise removal settings I use. Just to be clear, this noise does not appear in the entire audio. When it appears and I’m not saying anything, I don’t mind. I just remove it. The problem is when it’s together with my voice. I messed a bit with EQ and it removes it, but my voice gets strange, a little metallic.
Also uploading a piece of audio with the noise, and a piece with unfiltered audio, showing the background noise that I have when recording.
Any help on this case?
The top number, 40dB is way too high. That will produce sound errors and maybe brittle, honky voices.
You can’t use Noise Removal to turn your ratty, noisy recording into a studio production.
Noise Removal works in two steps. Step one is the Profile step where you select some of the noise by itself for Audacity to taste. Audacity will try to design filters and effects to remove anything in that profile or taste. It’s an insanely important step. If you catch a little of the actual show in that sample, parts of the show will vanish. If you miss something, that something will pop up after reduction. That appears to be what you have.
If your show is really ratty, you can’t tell what’s in the profile just by listening. This is the natural limit of the tool. If it’s that bad, you probably have no show.
Other limits are that it will not affect noises that constantly change. Audacity only knows about the exact, specific noise in the profile. If you have noises like a bus starting out in front of your house or a plane going over or train going by, those are now performers in your show. Moving or changing noises are very difficult to remove.
Nowhere is it written that you can’t apply Noise Removal more than once and avoid piling up all the reduction errors in one pass.
http://manual.audacityteam.org/o/man/noise_removal.html
If you do manage to pull this one out, look at recording in a better environment. Rescue shows always sound tight and cell-phony.
Koz
When it appears and I’m not saying anything, I don’t mind. I just remove it.
For that you can try a Noise Gate. A noise gate kills the audio completely when the level falls below a preset threshold. The advantage is that it doesn’t “touch” the audio where the volume is above the threshold. It should duplicate what you are now doing manually.
But, it’s also something you have to experiment with because it can be distracting when the background suddenly goes dead slient.
In Audacity it’s called “Gate”, and I beleive its one of the optional LADSPA plug-in effects.
If you can get noise reduction to work without side-effects, you shouldn’t need the noise gate.
Strange noise after noise removal
Sometimes it works great and sometimes “The cure is worse than the disease.” That’s why pros still record in soundproof studios with good equipment. 
Thanks for the replies. Don’t get me wrong, I was not looking for my recording to be like one recorded in a soundproof studio. Right now, I cannot have that, and I know the limitations that come with it. The sound in the background is my computer, I can manage to not record it at all, however the sound recorded becomes extremely low. I came here because like I said, I’m new to all this sound stuff, and really want to learn.
Never tried to do noise removal more than once, I always thought it was a one step thing 
definitely will try that. Thanks for the tip
Noise gate? it sounds complicated o.o
Well, I must say. You guys rock! Just followed Koz and DVDoug tips, and here’s the result =]
That came out well.
The sound in the background is my computer
This is one thing that kills you with USB microphones. You can’t get alway from the computer noise. You should put chairs around the computer and drape blankets or towels over them to minimize the noise as much as possible. Make a little fuzzy valley with the computer in the bottom. Put a towel on the floor, too. You can’t put a blanket over the computer because the heat would kill it.
I had to do that with a voice shoot at work once. You will have a tiny version of this “studio” I made once. Yes, those are furniture moving blankets.
http://www.kozco.com/pictures/boothFinished/laptop-mic.jpg
Note there’s a pad on the floor, too.
As good as you get with noise reduction and noise gate, it always sounds cleaner and more natural if you don’t have to do that. Not to mention you’re going to have to go through all those corrections with each recording. And you can’t change anything. If you do anything that changes the noises – change furniture, move the microphone – you have to set up Noise Removal again.
Koz