Sound acting weird?

Ok I thought my sound was high or sounded like it so I turned it down no change after changing it less and less it still sound the same until I put the master volume to 0 now there is only a loud drum sound left after I kill things or it will happen randomly can I get some help here?

once or twice the sounds has cut in and out on me.

For the most part though, haven't had any problems.

Finally found out what it sounds like. the count down in pvp wf like the final 10 secs of match thats what Im hearing all the time now Idk how to get it off either