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J. Perelman
"Entertaining physics". Book 1.
Chapter 10. Sound and hearing


Why insects often emit a buzzing noise? In most cases, they didn't have to do this no special authorities; hum, audible only when flying, simply due to the fact that, flying, insects swing wings several hundred times per second. The wing is oscillating plate, and we know that every often (usually 16 times per second oscillating plate generates a tone of a certain height.

Now you will understand how it was possible to learn how many strokes does per second when flying something or other insect. For this it is enough to determine by ear height published insects tone, because each tone has its own frequency. Using “loop time” was able to establish that the frequency of the wings of every insect, almost unchanged; adjusting the flight, the insect changes only the magnitude of the wave (the amplitude of the oscillation) and the tilt of the wings; the number of waves per second is increased only under the influence of cold. That's why the tone emitted by the insects in flight, remains unchanged...

Found, for example, that room fly (publishing in flight tone F) making a second 352 sweep wings. Bumblebee waves 220 times per second. Bee, emits a tone, flaps 440 times per second, when it flies freely, and only 330 times (tone)when flying Laden with honey. Beetles originating in flight lower tones, move the wings less promptly. On the contrary, the mosquito makes wings 500-600 vibrations per second. For comparison, note that the propeller of the plane makes an average of about 25 revolutions per second.

Entertaining physics J. Perelman


System Orphus


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