I recorded my audiobook in stereo, edited it (loudness normalization -20, limiter -3.5), submitted it to ACX, no problem. Then converted it to mono in Audacity, and now RMS is too low by as much as 4.6 dB. I figured since it is not really “stereo” just two identical tracts it would be no problem. Obviously there is some mysterious sound magic going on here. Is there any easy fix? Or should I just say screw it and submit the stereo version? Windows 10. Thanks!
[SOLVED] RMS to too low after converting from stereo to audio with audacity
Just loudness normalize again and everything should be OK. (Make sure to use RMS as ACX requires, not perceived loudness.)
It shouldn’t be necessary to limit again but you can if the peaks end-up too high. Any linear volume change makes the same dB change to the RMS and peak levels so I assume they are both 4.5dB lower after converting to mono.
Ideally, you go go-back to the WAV copy. When you open an MP3 it gets decompressed and if you re-export as MP3 you are going through another generation of lossy compression.
…I don’t know exactly where the -4.5dB difference came from but two channels together might “calculate” louder than one channel.
Thanks! When I looked back at my notes, I did need to amplify the stereo files by almost the same amount as the mono files (the largest difference in the low RMS was 3.9 dB (stereo) and 4.4dB (mono), but there was not enough “head room” to do so. Re normalizing and re limiting gave me enough “head room” to re amplify! I am not sure why I had to do it again. The normalize then limit then amplify steps must have been undone, when I converted to mono? Anyway seems to be working fine. I think this is a problem with not understanding how the tools you are using actually work!