I’ve been using Audacity for years for voice recording with my Blue Yeti mic - most recently with Ubuntu 16.04. I just moved up to Ubuntu 18.04 and installed Audacity 2.2.1 from the repo. Besides the version change, everything else - meaning the mic, computer, room, furniture, and voice (that’s me) - are all identical, but the quality of the recording had dropped significantly. Is it possible that the default out-of-the-box recording settings are different (I don’t remember having to change from defaults in the past)?
I’ve uploaded “before” and “after” examples to illustrate my problem. To make the comparison as accurate as possible, I performed basic noise removal on both files.
Your “new-example.flac” file shows substantial clipping (distortion) due to the recording level being too high.
First thing to check is the recording levels in Ubuntu’s volume control. If everything looks OK there, check the levels with alsamixer.
I think you’re right about the Ubuntu audio input levels. I dropped the level by half and the quality definitely improved - although the recorded output was barely audible. I raised the input level all the way back to full (with Over Amplification turned off, of course) and quality remained good - although a bit quiet (the wave forms are much smaller than usual).
It’s possible that I changed something else in between, but for now it seems that the recording quality is manageable.
I’ll keep digging - perhaps other new 18.04 users will run in to the same problem.