I had a dickens of the time trying to find out how to reduce the echo that is left after background noise is removed. However, I didn't give up and after playing with some of the settings, I believe I've figured it out! I'm using Adobe Audition CC (6.0). You'll want to follow the steps below as your method of noise reduction, not after the fact. So we're preventing the echo during noise removal, not getting rid of it...if that makes sense. So start with your original audio with the noise, then...
I hope that helps!!
May I make a suggestion? Although you're experiments were useful, trying to find a one size fits all "one pass" solution probably won't yield the best results. Basically if you can hear NR artifacts (the echoey quality you refer to) at any point, you've done too much noise reduction in one go.
Generally, you're better off doing 3 or 4 passes of very light noise reduction, grabbing a new noise sample each time. For most "normal" noise, it can also be very worthwhile to increase the FFT size (on the advanced menu) a preset or so before grabbing each of those sequential noise samples.
In fact, you generally don't want to take off very much at all at FFT4096. You can get way better results from much higher settings, almost regardless of what sort of noise it is. Since the FFT size essentially determines the window width, lower settings are really only much use on low frequency noise, and they are the ones responsible for most of the strange sounds you hear in the rest of the frequency range. The reason for this is that you get many samples of higher frequency sound within the wider window, and the processing simply can't do anything with it. The higher FFT sizes mean that signal slices with HF in get dealt with much more accurately, hence less 'bubbly' noise. The downside of course is that processing takes significantly longer.
So thanks for posting, ArialBurnz, but I'm afraid you've only just scraped the surface! Bob's method of doing multiple passes at different rates is definitely the way to do with Audition's NR, but you will always get better results in terms of remaining artefacts from higher FFT settings.
Confession: I'm brand new to Audition. I just learned to use it about 3-4 weeks ago. I'm recording a podcast and audiobooks (I'll post links later once they're live), and what I've heard so far with the experiment I had last night seemed to definitely serve my purposes. The whole "FFT" thing is Greek to me! LOL I'm a total newb at this.
Sounds like what you guys are talking about might be overkill for what I'm doing and I'm really pressed for time, so multiple passes and tweaking at such a minute level might be more than I need. I'm not knocking the advice at all, though! I appreciate the additional clarification.
I had a dickens of the time trying to find out how to reduce the echo that is left after background noise is removed.
Ah, well if you'd have asked us in the first place, we'd have told you immediately what to do! And it's not overkill - it doesn't take long and works miles better.
Right, if you want a quick fix then before you take your noise sample, alter the FFT setting to the highest it will go. Then take your noise sample. Now you will find that you have a lot more lattitude to play with before strange noises get in the way. The other thing that sometimes helps (although I don't think it will in your example above) is to shape the amount of NR - that's what the blue line is for. You can add points to it and drag it up and down. This will give you the opportunity to listen to where the most obtrusive noise is, and shape the response so that it attenuates more of that, and less where it isn't so significant. This also reduces the chances of artefact noise just to the band where you're taking most out. Because you've reduced the artefact noise anyway, you'll get away with a higher (longer) spectral decay rate, which should reduce any abrupt cut-offs - more important with speech than anything else.
The other thing that's sometimes worth checking is the 'output noise only' box during preview - this will rapidly show you when you're removing wanted signal as well as noise - but remember to remove the check before doing your actual processing - or you end up with only noise!
And also remember Bob's advice - take at least two swipes at it, using the highest FFT setting for one, and a lower one for the other. It doesn't matter which order you do them in, but you'll have to take a separate noise sample for each, because they are FFT-size specific.