Audacity Forum

Audacity files exported as MP3's have rumbling warbling type sound in quiet passages not present in the audacity file. Any thoughts?
Thanks

MP3 is lossy compression... What MP3 quality/bitrate settings are you using?

Do you need MP3?

For reference, the "best" settings are 320kbps CBR (constant bitrate) or 'V0" VBR (variable bitrate), and in either case, you should use "joint-stereo" (assuming your original file is stereo).

320kbps will make the largest possible (least compressed) MP3 file, so if file size is not an issue, you can go-ahead an use that setting. Otherwise, you can try lower-quality settings to see what's acceptable to you.

Note that we can't really say that 320kbps is "better" or "best" if it doesn't sound better. With most music, you can get away with somewhat lower-bitrate (smaller file) settings, and the MP3 will still sound like the uncompressed original. If 192 kbps sounds identical to the original, we can't say 320 is better! No matter what settings you use, virtually none of the bytes in the decompressed MP3 are the same as the original! but the idea is for the compressed file to sound identical to the original (unless you just want a smaller file without regard to quality). Some songs compress better than others... It mostly depends on the song and how good you are at hearing artifacts.

Thanks for that info.
My export settings for MP3 are 128kbs in stereo.
I never chose them. I presume they are the default.
I'll try 320kbs. What difference does joint stereo make ?