I have a playground under the window in the courtyard. In the afternoon, the kids are busy in the sandbox, and in the evenings the site was occupied by young alkonauts. Till late at night they get drunk, yell, swear - they prevent people from sleeping. Tired, I decided to disperse.
At home on the mezzanine wall lay two old self-made columns. He pulled out a woofer from one, found a circuit in old zahashniks, which was used to adjust the phase inverters in the speakers, and in a day assembled a simple infrasonic emitter tuned to a “fear frequency” in a plastic bucket case.
In the evening I hung the structure out of the window and turned on the power. Five minutes later, the drunkard as a cow tongue licked.
Now, as the noise rises - I turn on the pugach for a couple of minutes. In the courtyard - quiet, smooth surface and God's grace. And since the whole structure is a shout, it "blows" only into the yard, and not into the house. My dog doesn’t even howl.
Operating principle. The circuit is a self-oscillating generator operating at the natural resonance frequency of the loudspeaker suspension system. Since the resonant frequency of the woofer is 40-100 Hz, to reduce it, you just need to weight the suspension system. To do this, in the center of the diffuser you need to glue a coil of solder weighing about 20 - 40 grams, then the resonant frequency is reduced to 6-15 Hz. It all depends on the brand of the speaker, look at the parameters
Design. The circuit diagram is the simplest self-oscillating generator, which is launched from the speaker coil, I assembled it in the fifth grade, when I was making columns. Relay RES 9 to 5V, slowed by the operation of capacitor C1. In fact, this relay is needed to “push” the speaker and turn off, then the circuit operates at the resonance of the speaker coil. Transistors - any low-frequency medium power, always on radiators (I took two bottoms from aluminum cans from under the Coke). Power - 9V backup from a dead modem. Resistors R1, R4 - volume control - the circuit operates on a pendulum resonance, and although the electrician consumes about two watts, the output is at least twenty, and the speaker without them drives.The speaker is basically any bass, I have an ancient 10 GD-34 at 10 W, with a 4 Ohm coil, the resonant suspension frequency is 80 Hz. Be sure to put in the case to exclude the acoustic "short circuit". The case is a children's plastic bucket. At the speaker, I cut my ears with a jigsaw, stuck it in a bucket and glued the “Moment” around the perimeter.
Settings - CAUTION INFRASOUND !!! First, you need to assemble the system on the table and check the electrician, at first without weighting, when you turn on the power, the speaker should buzz at the resonance frequency. I earned with a half kick. If it doesn’t work out, play around with the capacitor. Then assemble the device in a bucket, stick the “Moment” on the gap between the speaker and the bucket, and coat the weighting coil with the “Moment” and glue it on the “Moment” to the speaker diffuser. Since I could not find a normal frequency counter, I set the “frequency of fear” of 13 Hz with an Lissajous oscilloscope and low-frequency generator. To do this, I fed 26 Hz from the generator to one input of the oscilloscope, and wires from the speaker to the other, Then, in order not to get 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 cut the weighting coil, until he received a double Lissajous. That's all. I don’t post the photo - the bucket is the bucket.