Ultrasonic Translator Detect Subliminals

Electret mike -> laptop with good sound card -> this software:

Good luck. But honestly I think this could go down as an urban legend.

Are you implying you would like to meet and provide a useful answer under my "Heavy Duty Faraday Canopy"?

Paul Henry

Yes, but who wants to walk around a supermarket with a laptop, even if it had a "good" (abnormally wide range) soundcard.

I am looking for a circuit for a compact device.

Paul Henry

So what do you have against aluminum foil?

John

Paul-

Check out the Crystal Set Society's MidnightScience Ultrasonics page, . If you contact them with your question, they may have some suggestions. They sell kits that may cost about the same as building your own. I think they will sell individual parts such as ultrasonic transducers.

As I understand, there are two types of receiver. One is a translator, the other converts signals to pulses and digitally divides them down to the audible range. Which is best may depend on the nature of your "subliminal message", but either should determine whether or not the message is there.

I seriously doubt there is any ultrasonic signal mixed with music in a PA system. PA speakers aren't very good at ultrasonic frequencies!

Fred

You can fold frequencies about some point by chopping the signal. The chopper can be a JFET, an analog signal switch (a set of FETs in a chip), or a balanced mixer. If you wanted to hear 50KHz, you could chop it at 45KHz to produce 5KHz. 40KHz would also produce 5KHz from a 45KHz chop, so this does make a complete mess of your signal. The advantage is that it's trivial to build, tunable, and it does convert the sound into something you can hear.

I built one a long time ago. You'll hear electronic power supplies, class D audio amps in electronics, metal squeaking/clanging, air whistling through nose hair, and tons of other stuff.

There's no chance of subliminal messages - a power level that penetrates an old ear causes intense pain for for a young ear.

It chaffs my skin.

Paul

If it's beyond the range of human hearing, how the hell do they expect people to hear it? ?:-/

In the subliminal stuff I screwed around with a few years ago, the text was simply 20 dB down from the main sound (generally some generic "relaxation" tape like ocean waves or whatever).

And I'm way skeptical that it has much effect anyway.

But if you insist on a down-converter, look for something like bat microphones, sonar, or doppler radar electronics.

Good Luck! Rich

If the audio is speech that's played back at a higher frequency, then unless it's put through some kind of time-stretching algorithm it's also going to be shifted in time, i.e. shortened. I don't see how anyone could make sense of such a high-frequency burst of audio, subliminal or not.

However, this does bring up the interesting topic of what measures retailers DO implement to affect customer behavior. I know there's a whole discipline at the intersection of psychology and interior design that attempts to manipulate shopper behavior based upon the physical layout of the store. For example, not putting items in a 5 to 10 foot "dead zone" right at the store entrance where research shows customers are less likely to notice them, or making sure the dairy section is diametrically opposed to the produce section, to ensure customers have to walk alllll the way around and have ample impulse-buy opportunities before they can complete their grocery list.

How about a portable digital recorder and highly sensitive microphone and walk around the store, then pass that recording thru the spectra software.

hamilton

Do you mean "chafe?" Chaff is a noun.

Cheers! Rich

That was supposed to be a joke son. Chaff IS al foil.

Paul

Posting for Owen Roberts who can't post directly to this group...

I'd like to hear more about this from someone who's experienced it. The website is all about what happens at 1KHz. I didn't find ANYTHING about frequencies other than 1KHz. I'd like to see plots from 20Hz. to

How does this work? My (mis)understanding is that the ultrasonic energy uses the nonlinear compression of air to mix two or more ultrasonic frequencies down to the audible region. The secret sauce is in predistorting the input so that it comes out the other end correctly.

The thing that scares me is this: How much energy does the ultrasonic wave have to have to compress the air enough to output 85dB of baseband audio? Do I really want to be sitting two feet from this emitter??? Sounds to me like deafness waiting to happen???

And this is just another way of producing audio. Has no bearing on the subliminal aspects. Yes? no?

And this perhaps:

Paul

Maybe look at ultra-portable ones? I think the iPhone used to have a rather low sample rate for audio but people supposedly have done hacks. Another option is to hack a digital dictaphone, place a highpass with a sharp cutoff in there so that you only record the alias signals. That ought to be small enough, and they are not expensive.

Should be more then enough bandwidth.

hamilton

You sure about that? Frequency Range : SHQ: 75 - 20,000 Hz HQ: 75 Hz - 17,000 Hz SP: 75 Hz - 15,000 Hz LP: 80 Hz - 3,500 Hz