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When one drops a pebble in a body of water, one can observe multiple waves emanating from the point the pebble came in contact with water. Be it because the water "jumps" up and comes back down, creating more waves or because the water does "up and down" motion, there are definitely many waves.

But when one snaps ones fingers, thus creating a wave in the air, there is only one clear sound, no multiple, diminishing snaps (unless there is echoes, but this is not a concern), unlike one would expect just by observing waves in water. Why is this?

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When you snap your fingers there are multiple sound waves, but the speed of sound is so fast you can't distinguish individual waves. The frequency of sound waves is around 100Hz to 10kHz so each wave completes one oscillation in 0.01 to 0.0001 seconds.

What you're hearing when you snap your fingers is the envelope i.e. the overall amplitude of the sound waves. When you throw a stone into still water you get an expanding ring of waves moving out, so at the centre it's still then as you move outwards you pass through the waves and beyond them the water is still again. Hearing the finger snap is the same as being struck by the expanding ring of ripples.

Ripples

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    $\begingroup$ For those of us lucky enough to be color-blind, your lines/text on the image are virtually impossible to read. Not that you should take the time to update it unless your feeling really bored, but something to think about in the future :) $\endgroup$
    – tpg2114
    Commented Dec 6, 2013 at 18:53
  • $\begingroup$ Oops sorry, it was done in a hurry. I'll improve it tomorrow. $\endgroup$
    – John Rennie
    Commented Dec 6, 2013 at 22:30

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