If YouTube been on the downlow pissing about with everybody's audio, no doubt that others may have been or do from time to time.
Have a read...
Have a read...
YouTube's new Dynamic Range Compression (DRC).
YouTube seem to be rolling out a new method of loudness normalization. Instead of only applying negative gain on tracks with above -14 LUFS loudness, it seems to be now also applying compression to all tracks regardless of LUFS / loudness value.
www.audiosciencereview.com