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Whispering Dishes

A large blue concave vertical dish sits in the corner with a large window to the left and a white wall to the right.
A panoramic photo of a courtyard with large umbrellas, tables and chairs and glass safetly railing. To the far left is a white wall and window with a large vertical blue dish, and to the right is a large red dish identical to the blue one. There are trees in the background.

Large, flat dishes reflect sound waves to certain points.

How it works

One person whispers into the focal point of one whispering dish, while a second person stands listening at the focal point of the second dish.

Things to try or ask around the exhibit

  • Is it easier to hear the whispered message at particular points on the dish?
  • What's the softest volume that you can hear within the dish?
  • Can you hear other sounds being reflected by the dish?

Background

The small tube is located at the focal point, which is the best spot for the dish to collect and refocus any sound that strikes the dish. The dish is a parabola shape. This special shape makes the sound bounce over to the other dish. The parabola shape of the other dish bounces the sound into its tube.

Finding the science in your world

Parabola-shaped dishes are used to collect and focus light waves, radio waves and sound waves.

Sometimes, parabolic dishes are used in solar cooking to concentrate sunlight and cook food positioned at the focal point. Satellite TV dishes also collect, concentrate and convert signals that allow households to watch satellite TV, while astronomers in observatories around the world use very large parabolic dishes to collect feint radio signals and light waves emitted by astronomical bodies many millions of kilometres away.