Hello!
The new version of Audacity (2.4.0) is very buggy when I use it to normalize and export my bought MP3s.
After normalizing them with the batch function I export them, using the VB0-Quality.
These art the bitrates after exporting with version 2.4.0:
And these are the bitrates after using the former version, 2.3.3:
The settings are exact the same!
Audacity 2.4.0 uses a more recent version of LAME.
So? Now I have to stay with the old version to maintain a good quality for my MP3-files?
So? Now I have to stay with the old version to maintain a good quality for my MP3-files?
A lower bitrate doesn’t necessarily mean worse sound quality. It does mean a smaller file so maybe it’s doing a better job of compressing. 
However, re-compressing MP3 does tend to degrade sound quality. If all you are doing is normalizing there are applications that can make volume changes without decompressing, such as MP3directCut (or MP3Gain for volume matching (There is a limitation that you can only make volume changes in 1.5dB steps without decompressing.)
Well, VBR0 says 220-260 kbit/s, and then I see these numbers. I can’t believe it’s the same quality.
Do they sound different from the original?
Check that you haven’t inadvertently enabled the “Force export to mono” option in the MP3 settings.
Those are approximations. VBR targets “quality”, not bitrate. It depends on the complexity of the sound or how “hard” it is to compress.
Just for fun I compressed a silent file to V0 and I got 31.9kbps.
If you want a specific bitrate you can choose the Average or Constant bitrate modes.
You can always do a [u]Blind ABX Test[/u].
The bass is less audible in the version with the lower bitrate. It’s more present in the other file, even without headphones.
I can’t check the “Force export to Mono” setting at the moment, because I reinstalled the former version.
Maybe it has to do with this? → https://www.audacityteam.org/audacity-2-4-0-released/
The new version has been withdrawn.
But is the new version of LAME in 2.4.0 so much different from the version used in Audacity 2.3.3?
As I said before: I used in both versions the same settings and I was really happy with the results of Audacity 2.3.3.
Thanks, that looks interesting.