my question is concerning united states patent number 5159703. can you
explain how it works and the different types(fm and am). does the
final modulated output have to be between 20 and 20k hertz? is there a
practical way to identify it if it is being broadcast in the air.

Hi arty468-ga,

The patent describes a way to modulate a desired signal onto a
high-frequency sound wave. The suggestion is that by doing so it would
be possible to convey subliminal messages into the brain.

Bear in mind that the Patent Office does not test whether designs such
as this achieve their stated purpose.

The carrier wave of 14500Hz (as mentioned in the patent) is a very
high frequency sound wave. As we grow older, our ability to hear these
very high frequences declines. But most ten-year-olds will easily hear
a sound wave of this frequency. It will sound like a very annoying,
very high-pitched mosquito. So if you want to know whether this signal
is being broadcast in the air, just ask a ten-year-old!

This carrier wave is then modulated in step with the sound wave that
is intended to be the subliminal message. For frequency modulation,
the frequency of 14500Hz is varied up and down in step with the
waveform of the subliminal message. Single sideband is more
complicated to explain, but in essence the 14500Hz signal is
eliminated and replaced by a signal displaced from 14500Hz by the
frequency of the message that we want to send. So, if we were
transmitting the sound of Middle-C on the piano (256 Hz), this would
result in a sideband signal at 14756 Hz (24500 plus 256) for "upper
sideband" or 14244 Hz (14500 minus 256) for "lower sideband".

For practical purposes, the final modulated output would need to be
between 20 Hz and 20 kHz. As sphynx99-ga points out in the comments,
anything beyond this cannot be effectively generated with hi-fi
equipment nor can it be produced from loudspeakers.

Although ultrasonic transducers could be used with higher frequencies,
we can be sure these signals cannot be perceived subliminally. After
all, ultrasonic remote control devices are in widespread use and
no-one has reported receiving subliminal messages (or any other
auditory signal) when their garage door is opened.

As to whether there is any way for the human brain to demodulate one
of these FM or SSB signals, the answer is "no". Some scuba divers use
ultrasonic SSB sound wave equipment to communicate, and would
certainly know about it if they could demodulate it without needing an
ultrasonic receiver.

Even if there was a way to "pick up" this signal subliminally, it
wouldn't be intelligible (either consciously or subliminally). That's
because our brain has no way to generate a matching 14500Hz signal to
demodulate the transmission clearly.

If you are in any doubt about this, borrow a ham radio receiver with
an SSB function and tune into an SSB radio signal. If you listen to it
as AM, you can sometimes make out what is being said (with a great
deal of effort). But if you switch to SSB mode you will find that you
must tune it in exactly to make it intelligible. A few hertz either
way will make it sound strange, and 14500Hz away it's just noise.

So, to summarise:

1. For all practical purposes, the signal would need to be between
20Hz and 20kHz in order to be generated by stereo equipment, broadcast
by loudspeakers, and to have any chance of being picked up by the
human ear.

2. It's not going to work for sending subliminal messages into
someone's brain, because even if we can hear it we can't decode it.

3. If you want to identify if ultrasonic audio signals are being
broadcast, just ask a 10-year-old.

Please request clarification if you require any further details.

Regards,
eiffel-ga


Google Search Strategy:

subliminal ultrasonic
://www.google.com/search?q=subliminal+ultrasonic

ssb ultrasonic
://www.google.com/search?q=ssb+ultrasonic

It'd be tremendously helpful were you to provide more than just a
patent number. You haven't really described what the invention
supposedly does. Can you, for instance, provide a weblink to the
patent itself?

http://patft.uspto.gov/netahtml/PTO/srchnum.htm

I used to do CAD-based NC laser programming. A typical customer would
provide thorough data on what they needed cut with the laser: drawings
with full dimensioning. If a dimension was missing, it was usually
inferrable from the given data.

   Occasionally a customer would just provide a printed copy of a CAD
file, with no dimensions given whatsoever. I'd call them up and ask
for dimensions. Their customer service department would ask around,
and apparently no one on their end would have any idea of the
dimensions. I would then say, "But you sent us a *CAD* drawing.
Someone on your end made the drawing on a computer, which means that
person input very specific numerical data to generate the drawing. If
you send a CAD drawing, that means someone in your organisation
*knows* the dimensions."

   It's the same in this case. Yes, I know you can go to the Patent
Office website and look it up. My problem is that If the OP found a
web page with the relevant information, then the OP knows full well
what the weblink is, and can do a simple copy & paste. It's not up to
everyone else to do an exercise in mind reading.

http://snipurl.com/toolazytodoithimself

"http://snipurl.com/toolazytodoithimself"

   You fail to get the point. I already looked it up a long time ago.

>> can you explain how it works and the different types (fm and am)

The patent describes a method to modulate audible sound using a
carrier frequency that is slightly above the audible hearing range for
humans.  I'm not sure if 14.5 kHz is truly inaudible, though.  Some
people (especially younger ones) may hear it as a high-pitched whine
when using FM.

The patent mentions both FM and AM SSB (single sideband, see
Wikipedia).  In FM, the carrier is constantly transmitted, but in AM
SSB, the carrier is suppressed, and only the sideband information is
transmitted.  You can detect AM SSB only when it is actively being
transmitted.

Refer to Wikipedia for descriptions for frequency modulation (FM) and
amplitude modulation (AM).


>> does the final modulated output have to be between 20 and 20k hertz

Yes, for two reasons:
1) Human hearing range  (gotta hear it to "get the message")
2) Stereo equipment capability  (gotta be able to produce it)


>> is there a practical way to identify it if it is being broadcast in the air

Sure, there are many ways to detect a 14.5 kHz noise source.  Computer
sound cards aren't quite up to the task, since they have a sample rate
of 44100 Hz or 48000 Hz - not quite enough to reliably spot a 14.5 kHz
sound.  Something like a microphone -> A/D converter -> FFT -> 14.5
kHz peak detector.  It's probably easier in the hardware domain, but
I'm CompSci, not an ElecEngr.

On another note - I'm not aware of any information that indicates the
human brain is capable of demodulating AM or FM signals, even if they
are audible.  Better keep your tinfoil hat on, just in case!

So, to summarise:

1. For all practical purposes, the signal would need to be between
20Hz and 20kHz in order to be generated by stereo equipment, broadcast
by loudspeakers, and to have any chance of being picked up by the
human ear.

2. It's not going to work for sending subliminal messages into
someone's brain, because even if we can hear it we can't decode it.

3. If you want to identify if ultrasonic audio signals are being
broadcast, just ask a 10-year-old.

Please request clarification if you require any further details.

Regards,
eiffel-ga