"What we call "sound" is really an onrushing, cresting, and with drawing wave of air molecules that begins with the movement of any object, however large or small, and ripples out in all directions. First something has to move—a tractor, a cricket's wings--that shakes the air molecules all around it, then the molecules next to them begin trembling, too, and so on.

Waves of sound roll like tides to our ears, where they make the eardrum vibrate; this in turn moves three colorfully named bones (the hammer, the anvil, and the stirrup), the tiniest bones in the body. The three bones press fluid in the inner ear against membranes, which brush tiny hairs that trigger nearby nerve cells, which telegraph messages to the brain: we hear. It may not seem like a particularly complicated route, but in practice it follows an elaborate pathway that looks something like a maniacal miniature golf course, with curlicues, branches, roundabouts, relays, levers, hydraulics, and feedback loops."

--from The Natural History of the Senses by Diane Ackerman