system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is there such a loud sound when we clap?
gpt
You're compressing the air between your hands rapidly, creating a pressure wave. Which is, you know, what sound is.

The best, loudest claps involve cupping your hands to trap more air between them. Your hands squeeze that air together before it rapidly expands again out through the gaps between your hands.  That rapid compression and expansion is the sound wave that your ears detect. The more air you compress, the faster you compress it, and the harder you compress it, the louder the sound will be.

Compare that to, say, clapping with wide open hands, palm against palm, and you won't get much of a sound, not matter how hard you clap, especially if you can get the heel of one palm into the center of the other so very very little air is trapped.  You'll get a smacking sound, but that's mostly the sound of your skin smacking and vibrating the air, rather than a good solid compression of air like in a proper clap.