# Listen to this

## Listen to this

Sound is energy that moves back and forth through the air in the form of vibrations. These vibrations spread outward as waves, like the ripples caused by a stone when it is dropped into rather still water.

The first experiment demonstrates the existence and energy of sound waves. Channelling the sound inside a tube concentrates the waves in the direction of the tube. By channelling sound toward a candle, you can use the energy to blow out the flame.

The second experiment is all about the strength of sound waves. It shows that sounds get quieter if their waves are allowed to spread out. Scientists say that loud sounds have large amplitudes (variations of range).

In the final project, you can investigate pitch or the range of sounds by making a set of panpipes. Low sounds consist of a small number of vibrations every second. Musicians describe these sounds as having “low pitch” but scientists report the sounds as “low frequency”. The panpipes show that pitch depends on the length of each pipe.

## How sound travels

### You will need:

plastic wrap, tube of card, rubber band, candle, matches.

## How sound travels

1. Stretch the plastic wrap tightly over the end of the tube. Use the band to fasten it in place. You could also use a flat piece of rubber cut from a balloon instead of the plastic wrap.

2. Ask an adult to light the candle. Point the tube at the candle with the open end 4 inch from the flame. Give the plastic wrap a sharp tap with the flat of your hand.

3. You will hear the sound coming out of the tube. It consists of pressure waves in the air. The tube concentrates the sound waves toward the candle flame and puts it out.

## Sound Waves

### You will need:

ticking watch, tube 2 x 36 inch long.

1. Place the watch close to your ear. You can hear a ticking sound coming from it. The sound becomes fainter when you move the watch away from your ear.

2. Place one end of the tube over a friend’s ear and hold the watch at the other end. The tube concentrates the sound and does not let it spread out. She can hear the watch clearly.

## How to make panpipes

### You will need:

scissors, wide drinking straws, non-hardening modelling material, card, tape.

1. Cut the drinking straws so that you have four pairs that are 3 and ½ inch, 3 inch, 2 and ½ inch and 2 inch long. Block up one end of each straw with a small piece of modelling material.

2. Carefully cut out the card to the same shape as the blue piece shown above. Fix the straws into place with the tape from long to short to sign with card as shown.

3. Gently blow across the tops of the straws. You will find that the longer pipes produce lower notes than the shorter pipes. The longer pipes have a lower pitch or frequency and the shorter pipes have a higher pitch.

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