sound_play performs pretty awfully on certain machines. I'm reporting this second-hand, as it doesn't happen on any of my machines. Every single time sound_play is called, the framerate drops by anything between 10% and 50% for about a second (which I'm guessing is because that's the duration during which the sound plays), making for a very erratic experience indeed.
Meanwhile reduce the sound quality of the wav to 22kHz or less, mono if possible. Especially for sound that you play at repetition like a single bullet sound comming out of a machine gun. I had the same problem with the framerate dropping to 5fps when 5 AI and the player had a machine gun in hand.
GMFMODSimple.dll is has no trouble playing 44kHz sound bites...
Mike.Daily, You can peruse and check how the sound system is initialized in GM... if you see a way to force software mode/disable hardware mode on initialization... Harware mode is usually the cause for this, a mode no longer an emprovement on the system since today's PC are fast enough to offer better or equal performance to hardware mode with less problem (and more features). I hear the fmod people will depricate their own hardware mode of their sound engine.