Lateral inhibition, surprisingly easy:

A brain cell that makes a lot of noise can stop other cells that are close from talking at the same time.

Fourier synthesis, not as easy:

When you hear a sound, little pieces of tight, heavy air or not packed, light air are hitting your ear. The way the inside of your ear moves can be used to figure out what the sound was like and make it again. We build things that are like big ears to make the sounds. The inside of the built ear pushes air so that it's tight and heavy again, instead of like before where the tight, heavy air pushed on your ear.

How far your inside ear part has moved at each moment can be drawn to make lines that goes up and down as it flies right. When a point of the funny line is in the middle, that shows the moments when the inside ear part wasn't moving or was moving between being more pushed inside or more pushed outside.

Given a funny line that shows what a sound was like, we can show how its shadow falls on different directions in the space of slowly changing lines that always look the same after you move along them a little way, or that much again, and so on. To do this though, you have to be able to state the area that lies between the middle line and the line that comes from the funny line times the funny line. Also, the repeating lines have to not have any shadow on each other. How big the shadow is between two funny lines is figured out using the inner-times game with the area finding game. The area has to be nothing.

There are lots of kinds of lines like this that people who study sound can use, but the most often used ones are like the shadows of point going along the side of a ring.

This was fun. For a similar exercise in explaining things with a restricted vocabulary see Guy Steele's lecture "Growing a Language". He begins using only monosyllabic words, introducing new polysyllabic words in terms of monosyllabic and previously defined polysyllabic words.