RUBBER BAND HARMONICA

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WHAT TO DO

1. Cut out four paper rectangles, each roughly 4cm x 1cm.

2. Fold each piece of paper in half down its length three times to give four folded pieces of paper, each roughly 0.5cm x 1cm.

3. Stretch the wide rubber band around the length of one of the lolly sticks.

4. Place one folded piece of paper on top of the rubber band at one end of the stick.

5. Put the second stick on top so that the piece of paper is sandwiched between the sticks.

6. Cut off any paper sticking out from between the sticks.

7. Wrap a thin elastic band around the paper and sticks so that the paper is held firmly in place.

8. Place a second piece of paper between the sticks, about 1cm along from the first piece of paper. Again, cut off any paper sticking out, and secure the paper in place with an elastic band.

9. Repeat with a third piece of paper placed about 2cm further along.

10. Repeat with a final piece of paper placed right at the other end of the sticks.

11. Hold the harmonica so that the rubber band is around the bottom stick and blow through the gaps between the paper dividers. You should get three different notes!

WHAT’S HAPPENING

Blowing into the harmonica makes the wide rubber band vibrate, causing the air particles around it to vibrate at the same frequency (you can also feel the vibrations with your fingertips). These vibrations pass from air molecule to air molecule, producing a wave that travels away from the harmonica. When this wave reaches your ears, you detect it as sound.

The harmonica’s paper dividers separate the rubber band into three different lengths. Blowing through the ‘holes’ between the dividers produces different notes because the different lengths of rubber vibrate at different frequencies. The frequency at which a rubber band vibrates is proportional to how tightly it is stretched, and inversely proportional to how long it is and how heavy it is. This means that shorter lengths of rubber vibrate at a higher frequency, producing a higher pitched note. Blowing harder doesn’t change the pitch of the notes, but should make them louder.