Making sound bounce
Sound waves bounce off hard surfaces such as walls and floors and
ceilings. Here is a way you can prove this by making sound waves bounce
around a corner.
Materials
cardboard
cardboard tubes (2, same size)
transparent tape
towel
watch (wind-up)
Save the cardboard tubes from two rolls of paper towels. Fasten the
tubes together with a piece of tape, as shown.
Arrange the tubes so that they form a corner. Place a folded towel at
the free end of one of the tubes. Then lay the watch on the towel. Put
your ear close to the free end of the second tube. Can you hear the
watch ticking? No? Try it another way.
Hold the piece of cardboard in a slanted position across the open space
between the tubes. Now put your ear close to the second tube. What
happens this time? Now you can hear the ticking. Do you know why?
The sound waves made by the ticking watch travel through the first tube.
But when the space between the tubes is open, the sound waves simply go
out the open end. There is no way for them to get into the second tube.
When you place the cardboard across the open space, the sound waves
bounce off the cardboard and into the second tube. The second tube
carries the sound to your ear, and you hear the watch ticking. And
that’s how you can make sound go around a corner.
