If you pluck a guitar string, the string vibrates. You probably wouldn’t hear much sound from just that small vibrating string. So a guitar body is built to take energy out of the string and transmit it as sound. Try this fun experiment to get an idea of how a guitar string's size and weight affect the sound.
When something vibrates, it makes the air around it vibrate, too. Vibrations move out in all directions as sound waves, moving the air backward and forward. When these waves make your eardrum vibrate, you may hear a sound.
The width and tightness of the rubber bands around your box will determine whether it makes a high or low-pitched sound. Heavier, thicker, or loose-fitting rubber bands vibrate more slowly, producing lower notes. A thinner or tight-fitting rubber band will produce higher notes.
Art by: Robert L. Prince