This sale is for FOUR 75-Watt (peak power) ULTRASONIC TRANSDUCERS. This is for those who need more power. Up to FOUR of these 75W transducers can be powered directly from our 240W Amp or 100W Generator. Frequency range is 10kHz - 30kHz, and it can be powered directly from any 240W extended frequency Audio Amp. Regular amps will work also, but only at frequencies below 20kHz. Impedance is 4ohms .
If used with our 100W Ultrasound generator, it should be used with a 4 to 20-ohm series power resistor, or use at least two transducers in series. That's because it has low impedance so it will overheat when driven from 12 volts. Four of them can be connected in series-parallel for more power.
Can be used for experimenting with ultrasound and as a Phasor pain field generator (by continuously sweeping frequency). That can be triggered by a trip wire or other sensor, and used as a security system to repel two or four-legged trespassers. The sweeping ultrasound can cause certain adverse effects like paranoia, severe headaches, disorientation, nausea, cranial pain, upset stomach, or just plain irritating discomfort. Great for animal control. Frequencies below 21khz affect humans, and above 21khz are for animal control.
It is WATERPROOF so it's perfect for outdoor use or even experimenting with underwater communication. We dunked one, and it worked while under water for half an hour without a problem. BTW, it's as powerful as 25kHz ceramic transducers that we used to sell and which were from NAVY submarines where they were used in arrays as sonar. These might work for that purpose also, although I wouldn't dunk them deeper than about a foot.
BTW, these are limited purchase so when we sell the small quantity we have, there won't be more.
Phaser technology is also basis of the LRAD(tm) crowd control devices which were recently used to defend US Cruise Ship against Pirates near Somalia (Nov. 2005). The main difference between the two is that LRAD(tm) uses Phaser frequencies modulated on a high frequency (50khz+) carrier to extend its effectiveness to 300 yards. In other words, the effects that Phaser produces at tens of yards, LRAD(tm) produces at 100's of yards. Here are a few LRAD(tm) pics:
"[For] most people, even if they plug their ears, [the device] will produce the equivalent of an instant migraine," says Woody Norris, chairman of the San Diego firm that produces the LRAD(tm) weapon. "It will knock [some people] on their knees." The new megaphone being deployed to Iraq can operate at 145 decibels at 300 yards, according to American Technology, well above the normal threshold for pain. The company posts a scenario in which Al Qaeda terrorists would run screaming from caves after being subjected to a blast of high-decibel sound from the devices, their hands covering their ears. Here's a link with more info about LRAD(tm). 145 decibels at 300 meters - Ouch!
There is one more way to experiment with ultrasonic air transducers like this one, and that is to try replicate the effects of LRAD(tm). For that you'd need two transducers. LRAD(tm) works on a principle that when you cross two ultrasonic beams (say 20 and 25 kHz), you generate the difference between the two (5kHz sound) originating at the point where the two beams cross. Or you could use two same frequencies (23kHz and 23kHz) and FM modulate one of them with voice or audio. And another way of doing that is to phase-shift one of the 23kHz tones instead of frequency-modulating it. That delivers sound to long distances and makes it appear that the sound originates right next to you or inside your head, even though you're dozens of yards away from the transducers. And with more power, distances of hundreds of yards can be reached, which is what LRAD(tm) does.
The actual LRAD(tm) uses a sweeping frequency in weapon mode, which can be simulated using our Phaser Sweep IC chip (in animal control mode) driving one side of stereo power amp, and driving the other input with a steady frequency (like 25 kHz). Then connect two air ultrasonic transducers to outputs of the stereo amp, and you should hear the sweeping frequency at the point where the two ultrasonic beams cross.
And here's a short quote from New York Times magazine:
"Most of the sounds under military consideration are classified, but some are approved for public consumption. One truly harrowing noise is that of a baby crying, played backward, and combined with another tone.
Nimbly holding a big black plate, Norris stands with me in an A.T.C. sound chamber. "LRAD can instantaneously cause loss of equilibrium, vomiting, migraines -- really, we can pretty much pick our ailment," he says brightly.
Norris prods his assistant to locate the baby noise on a laptop, then aims the device at me. At first, the noise is dreadful -- just primally wrong -- but not unbearable. I repeatedly tell Norris to crank it up (trying to approximate battle-strength volume, without the nausea), until the noise isn't so much a noise as an assault on my nervous system. I nearly fall down and, for some reason, my eyes hurt. When I bravely ask how high they'd turned the dial, Norris laughs uproariously. "That was nothing!" he bellows. "That was about 1 percent of what an enemy would get. One percent!" Two hours later, I can still feel the ache in the back of my head."
And yet another use of Ultrasound (around 17.5kHz) is to discourage loitering of teenagers around stores, because only teenagers can hear that frequency. It becomes very annoying for them after about 10 minutes. In UK the power level is limited to 75db, but I don't know about any limits on ultrasound in US.