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Ultrasonic IMD weapon used in Cuba????

Blumlein 88

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https://spectrum.ieee.org/semicondu...erse-engineered-the-cuban-sonic-weapon-attack

I personally think the high intensity microwave/radar explanation is more likely. The Frey effect.

Pulsed RF fields: Exposure to very intense pulsed RF fields, similar to those used by radar systems, has been reported to suppress the startle response and evoke body movements in conscious mice. In addition, people with normal hearing have perceived pulse RF fields with frequencies between about 200 MHz and 6.5 GHz. This is called the microwave hearing effect. The sound has been variously described as a buzzing, clicking, hissing or popping sound, depending on the RF pulsing characteristics. Prolonged or repeated exposure may be stressful and should be avoided where possible.

https://en.wikipedia.org/wiki/Microwave_auditory_effect
 

restorer-john

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The article is flawed IMO.

"Because of nonlinearity in the smartphone’s microphone, the ultrasound produced by-products at audible frequencies inside the circuitry of the microphone."

The 'non-linearity' is likely aliasing. Sample rate of the A/D in smartphones is only pretty low <44KHz. If the level of high frequency (out of band) is high enough (the 25K ultrasonic emitter), the decimation filter can't get rid of it all before it hits the A/D and aliases occur down in the audible band.

Using a smartphone to record ultrasound when it is clearly incapable of accurately quantising the signal in the first place is pretty dumb.

The tiny electrets used in smartphones are conventional in design and simply have a powered fet and a few resistors behind the element- nothing special.
 
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Blumlein 88

Blumlein 88

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Yes, I hope that someone in the gov't did more than that. Some good measurement microphone with more than 40 khz response surely they tried. If all that has been done is what is in the press then I would be very disappointed. I have a tiny little calibrated Dayton mic for plugging into smartphones like an iPhone which cost like $15 and it makes it to 20 khz then rolls off.
 

Brad

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As far as I’m aware the Smithsonian uses a similar technique for spatially specific audio descriptions of exhibits. Ultrasound beams interfere in the ear with a beat signal that is audible in the spot where the beams cross
 

restorer-john

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...Ultrasound beams interfere in the ear with a beat signal that is audible in the spot where the beams cross...

That phenomenon is not in dispute. It doesn't relate to using a low quality, low rate, A/D converter in a smartphone in an attempt to capture 25KHz+ ultrasound.
 
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