Something like this:
while phy get collision data()
a = phy get collision object a()
b = phy get collision object b()
if a = <id of your object> or b = <id of your object>
if not sound playing(<sound object>)
position sound <sound object>, object position x(a), ...
play sound <sound object>
If you don't have the "if not sound playing()" you'll get the sound trying to restart repeatedly which sounds wierd. There are a LOT of collision events. It would have been nice if the collision force functions worked, then you could decide if a collision was big enough to create a sound.