Hi, This is my first post here. My company recently developed a game simulating Newton's Cradle for the iPhone. I've got the visual physics portions working well. Everything reacts as it should. My problem is the calculation of the collision sound levels. Originally I was basing it off of impact force, the result was the balls in the middle that were not moving were each producing a loud sound. As opposed to the single sound heard when using a real newton's cradle and releasing only one ball. I then switched to using only force of the individual balls and subtracting the vectors from each other. This had similar results. I finally just used simple displacement values of collision pairs to determine the collision loudness. My question is... What is the correct way to calculate a collisions sound? In real life... do the balls not moving actually make a sound and it's just perceived as one sound? I have a video of it here. https://www.youtube.com/watch?v=http://www.youtube.com/watch?v=VH50emxBJ3w http://www.youtube.com/watch?v=VH50emxBJ3w" Sorry for the music, hopefully the collisions can be heard well enough. I hope this is not perceived as an advertisement. I'm seriously trying to figure this out as I want my product to be the best possible. Thanks for your time.