I have a playground under my window in the yard. In the afternoon: the kids are hung up in the sandbox "and on the evening the platform was occupied by the Alconauto-Mallet. Until late at night they drink, yell, swear, sleep, get bored, tired, decided to disperse.
Two old self-propelled columns lay on the mezzanine at home. I took out a low-frequency speaker out of one, found in old zagashniki a skeleton, which I adjusted the phase-inverters in the columns, for the case I assembled in the case of a plastic bucket the simplest infra-sound device, tuned to the "frequency of fear".
In the evening I hung out the structure by the window and turned on the power. Five minutes later, the alcoholic, like cows, licked his tongue. Now, as the noise rises, I turn on the Pugach for a couple of minutes. In the courtyard quiet, smooth and God's grace. And since the whole construction is a shout, it "blows" only into the yard, and not into the house. I do not even get a dog howling.
The circuit is a self-oscillating oscillator operating at the resonant frequency of the loudspeaker suspension system.
The resonance frequency of the woofer is 400 Hz, then to reduce it, you just need to weight the suspension system.
To do this, at the center of the diffuser, you need to paste a spiral from the solder weighing approximately 20-40 grams, then the resonant frequency is reduced to 615 Hz. It all depends on the brand of dynamics, look at the parameters in the internet.
Construction, Schematic diagram - the simplest self-oscillating oscillator, which is started from the coil of the speaker, I assembled it in the fifth grade when I was making columns.
Relay RES 9 to 5V, slowed down by the operation of capacitor C1. This relay is needed to "push" the speaker and disconnect, the circuit works on the resonance of the speaker coil.
Transistors are any low-frequency medium power, necessarily on a radiator (I took two bottoms from aluminum jars from under the Cola). Power - a laptop at 9V from the dead modem. Resistors R1, R4, volume control - the circuit operates on a pendulum resonance, and although the electrician consumes about two watts, at least twenty output, and the speaker without them goes pie-wise.
Speaker in principle, any LF, I have an ancient 10ГД34 for 10 W, with a coil for 4 Ohms, resonance frequency of the suspension is 80Hz. To put necessarily in the case for exception of acoustic "short circuit".
Housing plastic baby bucket. At the speaker, the electric jig sawed his ears, stuck it in a bucket and glued the "Moment" around the perimeter.
CAUTION INFRASOUND !!! First we need to assemble the system on the table and check the electrician, first without the weighting device, when the power is turned on, the speaker should sound at the resonance frequency. I earned a half a penny. If it does not, play around with the capacitor.Then collect the device in a bucket, glue the "Moment" gap between the speaker and bucket, and spiral weighting agent miss the "Moment" and on the "Moment" also glue to the speaker cone.
Since I could not find a normal frequency counter, the "frequency of fear" of 13 Hz was set up by an oscilloscope and a LF oscillator in the Lissajous figure. To do this, I fed 26 Hz from the oscillator to one input of the oscilloscope, and the other from wires 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 what happened. Then he turned off the power and began to slightly cut the weight coil until he got a double Lissajous.
That's all. I can not post a bucket - a bucket is a bucket.