I imported some AAC/M4A files, deleted a little silence at the beginning & leveled the volume using the “Amplify” option via Effect → Volume & Compression → Amplify
I then exported them back as m4a files. Later, to verify that I had leveled the sound in one I did the Effect → Volume & Compression → Amplify sequence again & the suggested volume adjustment was a small increase, perhaps something like +.148. I checked some others that I had also put in an “edited” folder & they all had small suggested volume increases.
I edited another original from scratch, leveling the sound, exported it & then when I reimported it into Audacity I got the same type of suggested volume increase.
It is not a big issue, but it surprised me a little as when I did the same using FLAC as the compression format it always comes back with a “0” recommended(?)/suggested volume adjustment.
As a side note, I had previously been exporting them as FLAC files, but found that since they had already been compressed into m4a format before I got them saving them in FLAC provides no better sound quality than exporting them back into m4a after editing (as discovered in this thread)
Even at max compression the FLAC files are substantially larger than reexporting them as .m4a:
FLAC file, 16 bit depth, 14400 kHz, Level 8 (best) compression
m4a file, 14.4 kHz, exported at 128 kb/s but saved at 192 kb/s
Having a tiny volume drop doesn’t really cause me any harm, I’m playing these through a stereo system for a tiny group at a liturgical service. The stereo can easily adjust the volume more than is needed. I just wanted to level the sound a bit so one hymn isn’t way louder than another. This way I can adjust the volume beforehand & not worry about adjusting it for each hymn as we go.
I was just curious about the difference between the two formats & was bringing it to your attention in case you weren’t aware.
I also noticed that the FLAC file is exported at 625 kb/s. I’m not sure why that is as the original was 128 kb/s.
I am on Windows 11 fwiw.
