[PD] "ping-pong" ball-like algorithm in PD

[type_non]

I knew the name of this algorithm, but i can't remember it now. Imagine a ping pong ball being droped in a table, where the noise that it makes becomes faster and faster (Aphex Twin has one music where he uses this in some beats). Does anyone knows how to implement this in PD or where can i find more info? 
 
Thanks in advance.

		
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