Sound and volume trouble

hi all

so i got an annoying problem that i cannot solve

when i join a TS server , no matter wich one, there is ALWAYS 1 person i cannot understand because his “volume” is like 0 … even if i right klick on his name and set volume to max
every other person i can clearly understand and they are also verry loud. but this one person is like his volume is 0

what can that be ?

seriously ? nothing and noone ?