It could be, I have seen this before, and it could be used in an inverse stereo or target mode BUT the transmissions would still be obvious unless using something exotic like satellite directed lasers and local transponders &/or implants of some kind, which would also then be physically aparrent. Such a device would hardly be wasted on humming at people -and also risk questions being asked at the minimum! It would also be resisted by shielding / not being line of sight, or target being underground. This effect would explain sensitivity to carrier switched microwave systems like Tetra but this is mood affecting outcome, as a by product [and worrying too!], but not something that would be heard, ocurring <20 Hz in UK.. Not sure about GWEN in the states though. I'm looking into getting old data from a defunct site- but suspect this will be another 'side effect' issue rather than anything malign- but certainly worth a look..
On Aug 12, 7:12 am, dboots <[email protected]> wrote: > http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=P... > > United States Patent 6,470,214 > O'Loughlin , et al. October 22, 2002 > > -------------------------------------------------------------------------------- > Method and device for implementing the radio frequency hearing effect > > Abstract > A modulation process with a fully suppressed carrier and input > preprocessor filtering to produce an encoded output; for amplitude > modulation (AM) and audio speech preprocessor filtering, intelligible > subjective sound is produced when the encoded signal is demodulated > using the RF Hearing Effect. Suitable forms of carrier suppressed > modulation include single sideband (SSB) and carrier suppressed > amplitude modulation (CSAM), with both sidebands present. > > -------------------------------------------------------------------------------- > Inventors: O'Loughlin; James P. (Placitas, NM), Loree; Diana L. > (Albuquerque, NM) > Assignee: The United States of America as represented by the Secretary > of the Air ( > (Washington, DC) > > Appl. No.: 08/766,687 > Filed: December 13, 1996 > > -------------------------------------------------------------------------------- > > Current U.S. Class: 607/56 ; 128/898 > Current International Class: A61N 1/08 (20060101); H04B 007/00 () > Field of Search: 607/55,56 600/559,23,586 128/897,898 > > -------------------------------------------------------------------------------- > > References Cited [Referenced By] > > -------------------------------------------------------------------------------- > > U.S. Patent Documents > > 3563246 February 1971 Puharick > 3629521 December 1971 Puharick > 4835791 May 1989 Daoud > > Primary Examiner: Schaetzle; Kennedy > Attorney, Agent or Firm: Skorich; James M. Callahan; Kenneth E. > > STATEMENT OF GOVERNMENT INTEREST > > The invention described herein may be manufactured and used by or for > the Government for governmental purposes without the payment of any > royalty thereon. > > BACKGROUND OF THE INVENTION > > This invention relates to the modulating of signals on carriers, which > are transmitted and the signals intelligibly recovered, and more > particularly, to the modulation of speech on a carrier and the > intelligible recover of the speech by means of the Radio Frequency > Hearing Effect. > > The Radio Frequency ("RF") Hearing Effect was first noticed during > World War II as a subjective "click" produced by a pulsed radar signal > when the transmitted power is above a "threshold" level. Below the > threshold level, the click cannot be heard. > > The discovery of the Radio Frequency Hearing Effect suggested that a > pulsed RF carrier could be encoded with an amplitude modulated ("AM") > envelope. In one approach to pulsed carrier modulation, it was assumed > that the "click" of the pulsed carrier was similar to a data sample > and could be used to synthesize both simple and complex tones such as > speech. Although pulsed carrier modulation can induce a subjective > sensation for simple tones, it severely distorts the complex waveforms > of speech, as has been confirmed experimentally. > > The presence of this kind of distortion has prevented the click > process for the encoding of intelligible speech. An example is > provided by AM sampled data modulation. > > Upon demodulation the perceived speech signal has some of the envelope > characteristics of an audio signal. Consequently a message can be > recognized as speech when a listener is preadvised that speech has > been sent. However, if the listener does not know the content of the > message, the audio signal is unintelligible. > > The attempt to use the click process to encode speech has been based > on the assumption that if simple tones can be encoded, speech can be > encoded as well, but this is not so. > > A simple tone can contain several distortions and still be perceived > as a tone whereas the same degree of distortion applied to speech > renders it unintelligible. > > SUMMARY OF THE INVENTION > > In accomplishing the foregoing and related object the invention uses > a. modulation process with a fully suppressed carrier and pre- > processor filtering of the input to produce an encoded output. Where > amplitude modulation (AM) is employed and the pre-processor filtering > is of audio speech input, intelligible subjective sound is produced > when the encoded signal is demodulated by means of the RF Hearing > Effect. Suitable forms of carrier suppressed modulation include single > sideband (SSB) and carrier suppressed amplitude modulation (CSAM), > with both sidebands present. > > The invention further provides for analysis of the RF hearing > phenomena based on an RF to acoustic transducer model. Analysis of the > model suggests a new modulation process which permits the RF Hearing > Effect to be used following the transmission of encoded speech. > > In accordance with one aspect of the invention the preprocessing of an > input speech signal takes place with a filter that de-emphasizes the > high frequency content of the input speech signal. The de-emphasis can > provide a signal reduction of about 40 dB (decibels) per decade. > Further processing of the speech signal then takes place by adding a > bias level and taking a root of the predistorted waveform. The > resultant signal is used to modulated an RF carrier in the AM fully > suppressed carrier mode, with single or double sidebands. > > The modulated RF signal is demodulated by an RF to acoustic > demodulator that produces an intelligible acoustic replication of the > original input speech. > > The RF Hearing Effect is explained and analyzed as a thermal to > acoustic demodulating process. Energy absorption in a medium, such as > the head, causes mechanical expansion and contraction, and thus an > acoustic signal. > > When the expansion and contraction take place in the head of an > animal, the acoustic signal is passed by conduction to the inner ear > where it is further processed as if it were an acoustic signal from > the outer ear. > > The RF to Acoustic Demodulator thus has characteristics which permit > the conversion of the RF energy input to an acoustic output. > > Accordingly, it is an object of the invention to provide a novel > technique for the intelligible encoding of signals. A related object > is to provide for the intelligible encoding of speech. > > Another object of the invention is to make use of the Radio Frequency > ("RF") Hearing Effect in the intelligible demodulation of encoded > signals, including speech. > > Still another object of the invention is to suitably encode a pulsed > RF carrier with an amplitude modulated ("AM") envelope such that the > modulation will be intelligibly demodulated by means of the RF Hearing > Effect. A related object is to permit a message to be identified and > understood as speech when a listener does not know beforehand that the > message is speech. > > Other aspects of the invention will become apparent after considering > several illustrative embodiments, taken in conjunction with the > drawings. > > What is claimed is: > > 1. A method of encoding an input audio signal a(t) to produce a double > sideband output signal having a .omega..sub.c carrier frequency, which > when transmitted to the head of a receiving subject, will by the radio > frequency hearing effect induce a thermal-acoustic signal in the bone/ > tissue material of the head that replicates the input audio signal and > is conducted by the bone/tissue structure of the head to the inner ear > where it is demodulated by the normal processes of the cochlea and > converted to nerve signals which are sent to the brain, thereby > enabling intelligible speech to be perceived by the brain as any other > nerve signal from the cochlea, the method comprising: applying an > input audio signal a(t) to an audio pre-distortion filter with an As > (f) filter function to produce a first output signal a(t)As(f); adding > a very low frequency bias A to the first output signal to produce a > second output signal a(t)As(f)+A; applying the second output signal to > a square root processor to produce a third output signal (a(t)As(f) > +A).sup.1/2 ; applying the third output signal to a balanced modulator > to produce a double sideband output signal (a(t)As(f)+A).sup.1/2 sin > (.omega..sub.c t), where .omega..sub.c is the carrier frequency; and > transmitting the double sideband output signal to the head of the > receiving subject. > > 2. The method of claim 1, wherein the As(f) filter function step > further comprises the step of de-emphasizing the high frequency > content. > > 3. The method of claim 1, wherein the further step of suppressing one > of the sidebands of the double sideband output signal is done > resulting in a single sideband modulation transmission. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en -~----------~----~----~----~------~----~------~--~---
