I must disagree with the 'dump the lever when you hear the horn regardless' argument. Awareness of an engine failure should be from the change in noise of the engine/sudden yaw/Nr sound changing - with the final clue being the Nr horn.
Suppose you inadvertantly let the Nr decay in the hover and the horn goes off - if you are conditioned (as many are) to slam the lever down in a Pavlovian response to the noise then you are going to hit the ground hard and probably roll over. I know because this is exactly what an owner with 150 hours on type did to me - the aircraft went back to California in a box, fortunately we didn't.
Listen to the aircraft and get used to the noises it makes, it might just save your life one day.