November 10, 2009 at 1:21 PM HST - Updated June 21 at 5:21 AM
Things you need:
Cut a piece of waxed paper large enough to cover the comb. Wrap the waxed paper around the teeth of the comb. Place the teeth side of the comb against your lips and hum a tune! This may take some practice, but keep trying. The waxed paper will vibrate, making a kazoo sound and will cause your lips to tingle.
Flatten two to three centimeters of one end of the straw, creasing the sides. Cut the ends of the straw into a triangle shape about one centimeter long. Put the triangle end of the straw in your mouth and press your lips gently down just where the triangle ends and blow. This might take some practice, but once you get it, you’re playing the straw oboe! Try cutting pieces of the straw off while you’re blowing. What happens to the sound?
How does it work?
Sound is caused by vibrations in the air. When these vibrations in the air reach your ears, your brain interprets them as noise. What’s causing your kazoo to vibrate? Touch your fingers gently on your throat and hum. Do you feel your throat vibrating? The vibrations are coming from the vocal cords in your throat. The air from your lungs flowing over your vocal cords causes them to vibrate. This causes the air in your throat and mouth to vibrate. These vibrations are transferred to the waxed paper on the comb. Because the waxed paper is loose and flexible, it distorts the vibrations from your mouth, making the sound of the kazoo different.
The two triangular pieces move up and down very rapidly, much like the reed in a woodwind instrument, like an oboe or saxophone. As you’re blowing, the air between the two triangles is moving very fast. For the air to speed up, it has to move from a high pressure area to a low pressure area. So the pressure between the triangles must be lower than in your mouth. This means that the high pressure air outside the triangles will push them together, closing them off. When the triangles close, the air can’t flow through, so the pressure inside the triangles increases, allowing them to open again. This cycle happens over and over, very rapidly, pushing tiny puffs of air out of the straw at about 50-100 times a second. This vibrates the rest of the air which you hear as sound.
As the sound flows through the straw, it travels up and down the straw, reflecting off both ends. That is why the pitch of the sound changes as the length of the straw changes. The shorter the straw is, the shorter the wavelength and the higher the pitch.