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 Subject: silent sound Category: Science Asked by: arty468-ga List Price: \$20.00 Posted: 16 Jun 2006 08:30 PDT Expires: 16 Jul 2006 08:30 PDT Question ID: 738697
 ```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.```
 Subject: Re: silent sound Answered By: eiffel-ga on 17 Jun 2006 14:02 PDT
 ```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```
 Subject: Re: silent sound From: qed100-ga on 16 Jun 2006 08:55 PDT
 ```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?```
 Subject: Re: silent sound From: flummox-ga on 16 Jun 2006 09:54 PDT
 `http://patft.uspto.gov/netahtml/PTO/srchnum.htm`
 Subject: Re: silent sound From: qed100-ga on 16 Jun 2006 10:23 PDT
 ```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.```
 Subject: Re: silent sound From: murunbuchstansinger-ga on 16 Jun 2006 11:09 PDT
 `http://snipurl.com/toolazytodoithimself`
 Subject: Re: silent sound From: qed100-ga on 16 Jun 2006 11:34 PDT
 ```"http://snipurl.com/toolazytodoithimself" You fail to get the point. I already looked it up a long time ago.```
 Subject: Re: silent sound From: sphynx99-ga on 16 Jun 2006 16:57 PDT
 ```>> 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!```
 Subject: Re: silent sound From: yeaphi-ga on 09 Aug 2006 08:58 PDT
 ```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```