mp3 reconversion - quality degradation?


This is a question for all the digital sound processing experts out there. I’m wondering what happens when you import an mp3 into Audacity (or any other audio program) then export it as mp3 at the same quality level (e.g. 128 kbps).

The first question: is it a simple copy from memory and save to disk operation? I assume not due to the copyright issues associated with mp3 encoder usage…

So if the program converts the sound to the digial waveform representation then back to mp3, is there sound quality degradation when compared to the original mp3 file? If so then to what extent? When does the “loss” become audible? What would happen if you repeated this import-export-re-import process 10, 100 or 1000 times - would you end up with a really distorted and/or noisy end-product?

On a more practical side, suppose I have an gigantic mp3 at 192 kbps quality which I want to split up (File-Export Multiple…). Is it a waste of space exporting the chunks as 192 kbps (in the interest of preserving best sound quality while keeping size small)? If you want to keep at least the same audible sound quality as the original, should you go up to 256? (Or if distorsions ARE introduced, how low is reasonable to go in bitrate?)

Hope my questions make sense. Thanks in advance.


Yes you will get additional degradation if you import an MP3 into Audacity and then export it again as MP3 - how perceptible this is depends on the quality of your equipment and your ears (age and sex are both factors here - young women have the best hearing typically).

To break up an existing MP3 into chunks, there are better and simpler tools availble to just cut the MP3 as it is without any decoding/recoding - a quick google of t’interweb should help you find one (probably free).


I use “MP3split” for this (free and cross-platform)