This project proves the existence of invisible sound waves through the evidence of motion. To create this project, place some dry rice or small pebbles on top of a drum. Hold another drum so that the head of the second drum is facing the first drum. Strike the second drum with a mallet four or five times in a row. The rice or pebbles will "jump" around on the head of the first drum due to the vibrations created by the second drum.
This project mimics a xylophone and illustrates how the amount of vibrating space affects pitch. Place three to five glass or plastic bottles in a row. Fill the bottles with different amounts of water. Blow across the bottles' tops one at a time and listen to the pitches created. If a bottle has less water, the pitch will be lower because there is more room for the vibrations inside the bottle. In contrast, if the bottle has more water, there is less room for vibrations and the pitch will be higher. Experiment with different water levels to create simple melodies on this homemade instrument.
This project demonstrates how the size and tension of a string affects the string's pitch. The principles in this project apply to creating music on stringed instruments. Simply stretch three rubber bands across the top of an empty coffee can. Pluck each rubber band to hear its pitch. Then pull each rubber band tighter with one hand as you pluck it again. The pitch will be higher this time, as greater tension on a string produces a higher pitch. Try rubber bands of different thicknesses. You will see that thicker rubber bands vibrate at a lower rate and produce lower pitches. Thinner bands vibrate more rapidly and produce higher pitches.
This activity illustrates the fact that a vibrating source must be present in order for sound to be produced. If the vibration stops, then the sound ceases as well. First, hum and touch your throat as you do so. You will feel your vocal cords vibrating. Then strike a drum with your hand, mallet or a drum stick. Do this several times, allowing the sound to ring out. Then place your other hand on the drum's head and strike the drum again next to your hand. You will hear a sound, but it will stop immediately since your resting hand is causing the vibrations to cease.