I have a playground under the window in the courtyard. In the afternoon: the kids are messing around in the sandbox ”and in the evening the site was occupied by alco-planters. Until late at night they get drunk, yell, swear, interfere with sleep, tired, decided to disperse.
The houses on the mezzanine were covered with two old self-made columns. He took out a low-frequency loudspeaker, found a scheme in the old zagashniki that she tuned into the phase inverters in the speakers, and in the case of a plastic bucket collected the simplest infrasonic device tuned to the “fear frequency”.
In the evening I hung out the design for the window and turned on the power. Five minutes later drunk, like cows, tongue licked. Now, as the noise rises, I turn on the pugach for a couple of minutes. In the courtyard, quiet, and God's grace. And since the whole structure is a horn, it “blows” only into the courtyard, not into the house. I don't even have a dog howling.
The scheme is a self-oscillating generator operating at a frequency of its own resonance of the loudspeaker harness.
The resonant frequency of the woofer is 400 Hz, then in order to reduce it, you just need to weight the suspension system.
To do this, in the center of the diffuser it is necessary to glue a coil of solder weighing about 20-40 grams, then the resonant frequency is reduced to 615 Hz. It all depends on the brand dynamics, the parameters look in the internet.
The design, the schematic diagram - the simplest self-oscillatory generator that starts from the speaker coil, I collected it back in the fifth grade when I was doing the speakers.
Relay RES 9 to 5V, slow to trigger capacitor C1. This relay is needed to "push" the speaker and disconnect, then the circuit operates at the resonance of the speaker coil.
Transistors any low-frequency medium power, always on the radiator (I took two bottoms from aluminum cans from under the Coke). Power - 9V backup from the killed modem. Resistors R1, R4, volume control - the circuit works at a pendulum resonance, and although the electrician consumes about two watts, the output is at least twenty, and the speaker without them goes hawking.
Speaker in principle, any woofer, I have an ancient 10GD34 to 10 W, with a coil of 4 Ohms, the resonant frequency of the suspension 80Hz. Be sure to put in the case to exclude acoustic "short circuit".
The case is a children's plastic bucket. At the speaker with an electric jigsaw, I cut down my ears, stuck it in a bucket and glued “Moment” around the perimeter.
CAUTION INFRAZVUK !!! First you need to assemble the system on the table and check the electrician, initially without a weighting agent, when you turn on the power, the speaker should ring at the resonance frequency. I earned with half a pint. If it does not work out - play around with the capacitor capacity.Then collect the device in a bucket, glue the “Moment” gap between the speaker and the bucket, and spread the helix coil with the “Moment” and glue the speaker to the diffuser with the “Moment”.
Since I could not find a normal frequency meter, I adjusted the “fear frequency” of 13 Hz with an oscilloscope and a low-frequency generator according to the Lissajous figure. To do this, he fed 26 Hz from the generator to one oscilloscope input, another from the speaker, then, in order not to fall under the infrasound, I covered the bucket, turned on the power for five seconds and looked at what happened. Then he turned off the power and began to slightly trim the weighting coil until he got a double Lissajous.
That's all. I do not post a photo of a bucket - a bucket is a bucket.