Stagnation Boss sounds aren't muted

Hi, I have my game sounds mute. Murgeth Bogsong is the boss name. When he winds up his big slam ability has very loud unmutable sounds. The ability sounds like lightning pounding in your ear :(

pls fix. I already never run stagnation but he shows up when running maven witness destructive play or forcing map bosses through scarabs.

I tested both natural spawn of him in his map, Stagnation and him being force spawned through the scarab "Domination Scarab of Terrors". Both have the same issue.