Noise Reduction Preview -- never finishes

I imported an MP3 file to attempt noise reduction on. After selecting a sample and performing the Get Noise Sample step, I tried to do a Preview before performing the actual noise reduction.

The first time I did this, I selected the entire track (approximately 25 minutes) then Effect > Noise Reduction > Preview. The remaining time listed in the pop-up kept increasing, so eventually I cancelled the process. Then I selected a smaller section of track (less than 2 minutes) and went through the same process. I left my computer for 5 1/2 hours, and the preview never went anywhere. The time remaining just kept increasing.

Since I have the original file elsewhere, I decided to select the whole track and simply perform the noise reduction on it without previewing. Audacity finished this in less time than it has taken me to type in this post.

So it’s not my computer, since it handled the actual noise reduction in mere seconds (and it turned out beautifully). Is this a bug?

I would really like to get the preview function to work. (Great software by the way.)


Mac OS High Sierra 10.13.6

Audacity 2.2.2

I meant to say that I imported an MP4 file. Not sure that makes a difference.

I’m not able to reproduce this problem.

Does normal playback work correctly?
Do other effects preview correctly?
Does previewing noise reduction fail on other Audacity projects, or just this one?

Normal playback works fine.
I tried a couple of other effects (vocal reduction and isolation) and they previewed just fine without delay.
At the moment I don’t have any other recordings on which to try noise reduction. I guess I’ll wait and see if it continues happening.

Are you sure it was an MP3? Audacity has no Clip-INFO, so you should Get Info to the clip before you import it and make sure it is what you think it is.


Looks like I never saw the last reply/question. As I said in one of my follow-ups, I was mistaken about it being an MP3 file. It was an MP4 file, I guess (it was so long ago now). I see that I have both MP4 and M4A versions of this on my computer.