What is the sound of two hands clapping?

Sorry for the cheesy reference to the Zen koan of one hand clapping.

I was trying to get my dog’s attention today and clapped my hands rather loudly. Where I clapped them happened to be very close to Mrs. Call’s ears and she was none too pleased.

But it got me thinking: from whence comes the sound? Please bear with me as I reveal my ignorance of acoustics and the like.

I know that if I record the sound of my clapping and play it back, the sound is reproduced by magnets thrusting a cone of paper in just the right way. This cone pushes a volume of air, and this push propagates as a wave, hits my eardrum causing it to vibrate in kind, and thus I can detect and identify the sound.

Why must my hands make contact to cause the sound? As my hands approach each other, there is (I imagine) a sandwich of compressed air between them. If I could stop short a nanometer before any contact, what if anything would I hear?

Is it that the contact causes my hand/arm to push a larger volume of air than was between my hands?

Quick experiment: :smack: Hmmm, sounds the same…

my wag is that until your hands are about to collide the air is poushed out slowly. However at the moment of collision the air is pushed out almost supersonically causing a crack