[Brainmaster07]

Yeah, I don't know if this is right, but this is kind of how I explained it earlier today at my Science Olympiad competition (Were going to state, woot):

Basically, when you hit something, it causes a vibration, which can vary depending on the force of the hit, material, etc. The wavelengths produced can vary from large, spread out wavelengths, which produces a low tone, or small close together wavelengths porducing a high tone. When these vibrations reach your eardrum, your eardrum reacts to the vibration, and sends the data to your brain. This makes you hear the sound.

I'm pretty sure that was right, lol. Eardrum thing is pretty vague though :P.