Flacko has written
I remember there was an option to disable that.
I'd personally never disable it because it acts as a warning when your team mates are engaging the enemy.
Edit: It's hud_fireinthehole, set it to 0
i know but is annoying when you are on other side of map and you head fire in hole so many times dc can you just make when we are 5-10 ft. away to hear it