if you google SSSS and HDTV you'll find all the theories on this

here's the sight where I found this:
http://proliberty.com/observer/20090118.htm

the article contains, among other observations:
"Newsweek magazine reported July 30, 1990, that the U.S. military successfully deployed "Silent Sounds" through the FM frequency radio band used by the Iraqi army after Saddam’s military communications system had been destroyed by coalition forces. "According to statements made by captured and deserting Iraqi soldiers….the most devastating and demoralizing programming was the first known military use of the new, high-tech type of subliminal messages referred to as ‘ultra-high-frequency silent sounds’ or ‘silent subliminals,’" Newsweek reported.
Once system-wide conversion to HDTV is made, the silent sounds that neutralized the Iraqi army can be planted into the minds of Americans enjoying the crisper images and richer sounds of digitized TV. Through HDTV, "Big Brother" will be able to order troops to invade the homes of America and begin seizing weapons, food, valuables and maybe even children while our people are absolutely paralyzed for no apparent reason and can do nothing to defend themselves, their families and their homes."

US Patent #5,159,703 which describes the "Silent Sound Spread Spectrum (SSSS)," was developed for military use by Dr. Oliver Lowery of Norcross, Georgia and granted on Oct. 27, 1992.

SSSS, or "S-Quad," is described in the abstract as, "A silent communications system in which nonaural carriers, in the very low (ELF) or very high audio-frequency (VHF) range or in the adjacent ultrasonic frequency spectrum, are amplitude—or frequency—modulated with the desired intelligence and propagated acoustically or vibrationally, for inducement into the brain, typically through the use of loudspeakers, earphones, or piezoelectric transducers. The modulated carriers may be transmitted directly in real time or may be conveniently recorded and stored on mechanical, magnetic, or optical media for delayed or repeated transmission to the listener."

In layman’s terms, this device, this "Sound of Silence" simply allows for the unwarranted implantation of specific thoughts, emotions and even prescribed physical actions into unsuspecting human beings"

actually, turning over analog to hidef TVs has been in the works for at least two decades - more, really. I remember going ot conferences on this at NAB conventions when i was a trade reporter in the early 80s. it took this long because the standards around the world were all in conflict, with America's being the lowest.

someone wrote back to a youtube video about this:
"regarding the switchover to HDTV and the converter boxes. It has nothing to do with SSSS. You are reaching. I have Lynx 24 bit192k converters and the best spectrum analysis software available. There is nothing extra there. Period. If you want to chase mind control science look into the reason for the 60 HZ refresh rate for a 30 second framrate. You are kind of retarded and have no idea what you are talking about."