problems importing/exporting mp3s

I am having problems importing an .aif file mixed in Reaper, having it show the correct db level in audacity, then trying to export it as a 320kbps mp3 and having the db levels go up by anywhere from .5 - 1 db. it’s unpredictable the outcome

I get a similar result when I mix the same file in Reaper as an mp3, the same file that would come out as a certain DB level as an AIF file comes out as an unpredictable higher level when mixed as an MP3 in Reaper.

The Tech Heads at the Reaper forum have not been able to help me so far.

What is going on? This wasn’t happening in February!


My guess is that you have strongly applied peak limiting to the audio.

Heavy compression / limiting will tend to flatten the tips of peaks. Because MP3 is a lossy compressed format, the MP3 data is only an approximation of the original. A characteristic of the MP3 compression algorithm is that when processing heavily limited audio, it has a tendency to overshoot the flattened peaks, which causes a small increase in the peak level.