I can confirm too this workaround removes the echo for me, or at least makes it not noticeable anymore for me. I got curious when I read this and I tried to replicate the issue by lowering the voice volume and creating a savegame in the first (tutorial) dungeon and returning to the main menu, loading again, etc. After some load-return cycles I have an echo in the character selection screen which then can be removed again by the "full-volume" workaround.
I was contacted from Larian support today regarding this issue and they asked me some questions about it. I answered them and send them my findings above and pointed them to this thread. So they are aware of the problem so I have high hopes this will be patched out soon.
