Do you mean it should play only one sound in total for all instances? I am guessing so from what I'm reading as you describe multiple instances of the sound as incorrect. If that's not what you meant, then what you are hearing is correct, it's trigger once for 'each instance'. To do one sound triggered for all instances you could try starting a very short timer and then add a condition to play the sound only if the timer is not running. I am not 100% sure if it'll work since collisions are detected in the same tick and they may all be before the timer begins in the same tick.