Sound bug with Legion

https://ibb.co/2WFXynJ (btw image feature didn't work with this)
Here are my sound settings. Sound effects, music, ambient sound, and dialogue volume are set to a minimum. I intentionally do not hear any effects except for item filters and trades when playing, as I prefer to play with music.
However, when the legion encounter is on the map, there's a thunder-like sound that happens very noticeably and loudly, which I usually notice when the templar army is present.