If Junior is looking for a science fair project involving acoustics, then this one from a hundred years ago will fit the bill. It’s simple to create but has a spectacular result. And as an added bonus, it promotes communication despite social distancing, since it is possible to whisper to someone about 20 feet away.

The diagram above is more or less self-explanatory. Two umbrellas are carefully placed on chairs as shown, and they serve as parabolic reflectors. The alignment is very critical, and it is recommended that a piece of string be used to keep the umbrellas exactly in line. In addition, each umbrella is thoroughly soaked in water, as this ensures that sound is completely reflected. While Junior whispers into one umbrella, the sound is heard by someone with their ear at the focus of the other umbrella. The sound seems to come from the closest umbrella.

The diagram and explanation appeared a hundred years ago this month in the March 1921 issue of Science and Invention.  The idea had been sent to the magazine by S. Leonard Bastin.

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