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Here, a water bottle and a paper tube make a membranophone—an instrument that produces sound from a vibrating stretched membrane. Kazoos and drums are both examples of membranophones. This one sounds a bit like a cross between a saxophone and a clarinet.
Now that your instrument is complete, simply blow into the straw on the side of the bottle, and your Water-Bottle Membranophone should play!
To make different sounds, you can add finger holes. To do this, pinch the paper tube slightly and cut out a diamond shape. Repeat to make more finger holes.
Membranophones are instruments that make sound from the vibrations of stretched skins or membranes. Drums, tambourines, and some gongs are common examples of membranophones.
In this Snack, as you blow into the straw, you create pressure in the space between the outer wall of the construction-paper tube and the inner wall of the water bottle. That pressure forces the membrane to rise, allowing air to flow into the top of the tube and escape out the bottom.
As the air escapes, the membrane returns to its initial position. But as you continue blowing air into the instrument, you force the membrane to rapidly rise and fall, over and over again. If you place your finger over the top of the membrane, you can feel it vibrate. These vibrations produce sound.
Opening or covering the finger holes changes the pitch of the sound. That’s because opening a hole has the same effect as shortening the length of the “pipe” (the rolled-up construction paper). The shorter the pipe, the higher the pitch of the sound.
Kazoos are membranophones that modify sounds when you speak or sing into them. Instruments like these are known as singing membranes.
Of course, your eardrum is also a membrane that reacts to the vibrations of sound. Air waves get your eardrum moving, and those vibrations are passed through your middle ear to your inner ear until, ultimately, your brain perceives the vibrations as sound.
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Attribution: Exploratorium Teacher Institute