It sounds like you actually do have a pretty good sense of what’s causing this! You’re triggering the Play Sound at Location somewhere you know will get hit for every line trace, and you know that’s not the behavior you want.
(Is the decreasing enemy health currently working the way you intended? If not, changing where the Event Hit Enemy is triggered will probably fix both those problems.)
But regardless - what you could do is put the audio play command at the end of that For Loop, which would guarantee the hit sound can only play once per gun shot. Could use a boolean or something to keep track of if any of the Line Traces hit the actor, then use that to determine if you want to fire a sound or not.