For dog ears only. Drawing, description

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For dog ears only. Children's Science Lab

Children's Science Lab

Hunter-poachers invented the ultrasonic whistle hundreds of years ago, but they were able to explain why dogs hear it, but the huntsmen do not hear it, much later.

It was only in the XNUMXth century that it was established that sound is air vibrations. In the XNUMXth century, devices appeared that measured the frequency of sound vibrations.

For dog ears only
Rice. 1. Galton whistle and its device

The English scientist Francis Galton in 1883 created a device that creates a sound of exactly a given frequency (Fig. 1), resembling a whistle in design. With its help, it was possible to find out that the ear of most people hears sounds with a frequency of no more than 20 Hz. Sounds of higher frequencies became known as ultrasounds. They are heard, for example, by cats, dogs and horses. They perceive sounds with a frequency of 000 - 20 thousand Hz, but bats break all records. For them, even 30 thousand Hz is not the limit.

Today poachers don't need ultrasonic whistles. But they still find application.

At the beginning of the last century, the famous trainer M.A. Durov showed a horse in the circus arena in Moscow that could add and multiply integers and even extract roots. She responded with a kick of the hoof. Moreover, the trainer was seated behind a screen, given examples in writing, and the horse perceived them telepathically and gave the correct answer. Moscow was shocked.

Having a little fun, M.A. Durov revealed his secret. In the artist's pocket was a rubber bulb with Galton's whistle. Imperceptibly pressing it, the maestro gave the horse a signal that no one but her could hear. And she, know your business, at the same time tapped with her hoof, which the audience took for a digital code ...

During the Second World War, the Japanese found Galton's whistle more serious use. During the Pacific War, the Americans repeatedly captured small Japanese ships. The team gave up, leaving intact all the most important things: weapons, provisions, engines. But over and over again on the captain's bridge they found fragments of some device, consisting of a tin horn and pipes.

American intelligence officers, whose attention had long been attracted by the ability of Japanese ships to act in concert, without resorting to any known means of communication, having put together the fragments of a device broken on different ships, found out that they had a fundamentally new means of communication in front of them. It was based on a powerful ultrasonic whistle, powered by compressed air from a ship's compressor. With the help of a special ultrasound device, the captain's voice changed in time with the sound vibrations. Modulated ultrasound was sent to the addressee with the help of a horn.

The received signal was processed by subtracting the carrier frequency, and a human voice became audible. The range of such a communication system reached several kilometers.

For dog ears only
Rice. 2. Referee sports whistle

But let's talk about whistle designs. Let's start with the simplest (Fig. 2). Take two strips of tin. Bend one of them, as shown in the figure, in a zigzag, and the other with a bracket and solder together. If you pinch the side holes of the product between your thumb and forefinger and blow into the tube, you may get a whistle. If the whistle is silent, you will have to do the adjustment. It consists in finding the correct position relative to the flat tube of the end of the cylindrical part of the whistle. A clean and loud whistle is produced when a jet of air enters the cylindrical part, makes a turn around it and deflects upward the air flow coming out of the tube. The flow in the cylindrical part stops, but after a moment the barrier disappears; a new portion of air enters the cylindrical part, makes a revolution along it, and everything repeats. As a result, a stream of air comes out of the whistle slot, interrupted with a high frequency. He creates sound.

After the first successful experience, make several whistles with a cylindrical part of different diameters from 5 to 20 mm. The smaller the diameter of the cylindrical part, the higher the frequency of the sound. A whistle with a diameter of less than 5 mm can already produce ultrasound. Only you will not hear it, so you will have to set up such a whistle with an oscilloscope and a microphone. You will see ultrasound on the screen as a segment of a sinusoid. The whistle is adjusted until its maximum amplitude is obtained. Well, if you don't have an oscilloscope, try to find a common language with a cat or a dog...

For dog ears only
Rice. 3. Boat horn device

The described whistle is easy to manufacture and adjust. But a cylindrical whistle is much more effective (Fig. 3). With a length of about a meter, it gives a sound with a frequency of 100 - 150 Hz and can replace the whistle of a steamer. With a length of several millimeters, the whistle will turn into a Galton whistle with a frequency of up to 60 Hz.

For dog ears only
Rice. 4. Whistle to control models: 1 - adjusting screw; 2 - piston; 3 - resonator (resonant cavity); 4 - insert forming an annular slot; 5 - sound reflector; 6 - air tube.

In Figure 4, you see an ultrasonic whistle designed to control models. It is powered by a rubber bulb and is equipped with a parabolic reflector that directs the sound to a distance of up to 25 m. Having trained the dog to respond to its sound, you can show various tricks with it.

Author: A.Ilyin

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