|Energy & Forces - Properties & uses of energy - Light & Sound - P4G10
1. The children will be willing and able to produce a wide range of sounds with little prompting from you! Allow them to try out the school instruments paying particular attention to the way the sound is produced.
2. Remember for this lesson the important point is that sound is linked to vibration. A surface vibrating causes the air above it to vibrate. That in turn causes the next layer of air to vibrate - a bit like ripples spreading out in a pond.
When the vibrating air reaches our ears, it enters through the outer ear and makes a membrane inside our ear vibrate - the ear drum. Tiny bones touching the ear-drum pick up the vibration and nerve cells attached to them interpret the vibrations as sound.
(See Sound cannon below for a demonstration of a vibration travelling through air.)
Another useful demonstration is to take a drum - or make one using a cut off balloon stretched over a cardboard tube - and place a few grains of salt or sugar on the stretched surface. With your mouth about 10 cm from the surface, sing a low note - you should see the grains jumping about as the skin vibrates.
Try making other noises nearby - which gives the most vibration?
The children can use worksheet C11 (G) to record what they made a noise with, describe the sound they made and what was actually vibrating.
To show how sound travels through air as a pressure wave starting at the source and ending at your eardrum, you could make a simple sound cannon as follows.
Take a sturdy cardboard tube such as a whisky or ‘Pringles’ tube and cut off the fixed end. Replace it with a cardboard disk from which a small circle - about 2 cm diameter has been cut out of the middle.
Cut the neck off a round balloon and stretch the remaining bit over the open end of the tube.
Fix in place with an elastic band.
By tapping on the stretched balloon, a ‘bullet ‘ of air can be sent out of the other end of the tube and used to blow out a candle from a distance of about 50 cm.
If you are not happy about using a candle in the classroom then make a clothes lines with pieces of tissue strung along it which will flutter. See Safety.