Weird Sound Bug Please Help Me

hi guys after the new 7.8 patch i started getting a weird sound bug were all the sounds are kinda faint and sound weird when i buy things in game or use abilities. I tried deleting lol and also the in game fixing tool three time and it works for a bit but ends up coming back. Im pretty sure this happened a few months ago too but i dont remember lol. Any clue how to fix it?? Thanks :)