Sound cannon
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.
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