Using Audacity 3.7.7 on an IBM Win 11. We get mp3 files from clients with 32-bit variable Format, but our system needs 16-bit fixed. I use the right click on the track to translate to 16 bit fixed, export, but it stays as 32 bit. I then exported as WAV 16 bit, which works, but our system requires mp3. Re-exporting at 16 bit for mp3, it looks successful until I reopen the saved mp3 file. It reverts back to the original 32 bit variable. Help, please, it only started having this problem after a recent update.
I have set Preferences/Audio Settings to default 16-bit, sample rate 44.1K
MP3 files don’t have a bit depth because individual samples aren’t stored.
And by default, everything you open in Audacity gets converted to uncompressed 32-bit floating point, (Floating point is better for editing/processing.)
MP3s have a sample rate (i.e. 44.1kHz) and a bit rate (i.e. 256kbps).(1)
You CAN have a bit rate of 16 or 32kbps but it’s “low quality”. The lower the bitrate, the more data is thrown-away to get a smaller file.
NOTE - Ideally, you should avoid editing MP3 and compress to MP3 ONCE as the last step. The MP3 gets decompressed when you open it, and if you export again as MP3 you are going through another generation of lossy compression and some “damage” accumulates. It’s usually not terrible (if you keep the same bitrate) but it’s something to be aware of.
There is a special-purpose editor called mp3DirectCut that can do some limited editing without decompressing.
(1) Besides constant bitrate, there are 2 variable bitrate options:
VBR (variable bit rate) let’s you choose a “quality” and LAME decides moment-to-moment what bit rate is needed.
ABR (average bit rate) let’s you choose the overall average bitrate (which lets you control file size) and LAME uses a higher bitrate with complicated sounds and a lower bitrate for simple sounds or silence. ABR analyzes the whole file in advance to best allocate the bits.
