# Ringing sound when you flip a coin?

When you flip a coin, you hear a ringing sound. I know that the source of the sound is the thumbnail hitting the coin, but it seems to be filtered by the spinning of the coin. Specifically, the faster the coin spins, the smoother the tone and it seems the spectrum becomes more uniform.

So my question is, physically, what is the exact phenomenon that is causing the filtering? It seems to be some form of frequency modulation (or amplitude modulation? I suspect it's the former but I could be wrong).

my other question is, what are the exact characteristics of this filter? I know that the filter will be a function of the angular frequency of the coin, which I'll call $\omega_m$, but other than that I don't know where to start on how to characterize it.

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Anyone have a microphone, a computer, a thumb and a coin? –  Kyle Jun 13 '13 at 15:58
A little searching reveals this, of which I can't say whether it is related or not. Perhaps somebody can make something of it in the context of this question. –  Glen The Udderboat Jun 13 '13 at 17:07
this question and its answers discuss the sounds of coins at length. –  alemi Jul 22 '14 at 17:47