Exhibit: Whisper Dishes
Sound waves are produced in the air when you speak. They are caused by vibrations of your vocal chords which open and close rapidly, releasing puffs of air from your lungs. If a sound wave strikes a smooth surface it will be reflected, in the same way that light is reflected off a mirror.
The plastic cones in front of the dishes are located at the focus of each dish. Sound waves starting from there spread out like ever increasing spherical bubbles until they strike the dish. The curve of the dish collects the waves so that they travel in a straight line away from the dish.
When they reach the second dish, exactly the reverse process occurs: the waves are collected by the dish and converge on the focus, to the listener’s ear. So even if you only speak softly, a lot of the sound waves reach the listener and the message is able to be heard clearly.