I first noticed it when I had to turn my speakers beyond the 25% mark which is usually the point in which (I feel) 'true sound' is achieved before things sound too loud.
It seems as if all normal sounds are cut down in half? if that makes any sense. And recently I noticed that I am suddenly having to bump all my sounds up pretty much to max to hear everything, as I looked further into this I notice that on my windows sound mixer levels meter all of my sounds do not match what usually happens at all. I am a twitch streamer who is constantly paranoid/paying attention to my sound levels when streaming so I notice any slight sound changes.
I am running windows 10 pro 64 bit, I use logitech z623's for sound plugged into rear 3.5 jack of my X99-A II motherboard. Alright so I recently ran into an issue that I have only noticed very recently because of specific circumstances.