That may answer why they use white noise as the cover: The frame and other components transmit enough vibration as to make a vacuum approach not very effective. I like the bullet proof glass piece. At least these folks are under no illusion as to the value of their services. -TD
Date: Tue, 21 Oct 2008 17:31:08 -0400 To: cypherpunks@al-qaeda.net From: jya@pipeline.com Subject: RE: Emanation Shielding with Music
Thanks for the comments here. Two responses received from elsewhere:
No. 1
Comments concerning TEMPEST and Laser Mic probes of windows and fenestration.
1. A high security internal and external window install would typically consist of two layers of 0.75 inch glass with a high lead contact. Exterior facing walls may have ballistic glass of varying thickness, again with a high lead layer.
2. Music IS NOT introduced between layers in a high security application. However, WHITE NOISE is introduced; sourced from a very secure high entropy white noise generator whose output is constantly monitored and mathmatically analysed in order to detect any unacceptable departure from the expected levels of entropy.
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No. 2
US patent 6,285,773 discloses a speaker designed specifically for use in double glazing.
Also interesting, five US patents assigned to CPFilms Inc. (7,405,872, 7,295,368, 7,177,075, 6,891,667, and 6,859,310) contain this golden nugget:
"A flexible transparent sheet made in accordance with this invention may also be used to minimize acoustic transmissions from a building by carefully applying the film to the window with an adhesive while making certain that no visible air bubbles are formed between the flexible sheet and the glazing of the window. The term "visible air bubbles" used herein means air bubbles which are visible without any magnification (i.e., visible to the naked eye). It has been discovered that when the transparent flexible sheet lies over an air bubble, the flexible sheet behaves like the diaphragm of a loudspeaker. This causes unwanted transmission of sound waves. Avoiding these bubbles minimizes the transmission of the sound waves through the window."
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We add that the glazing must be acoutically isolated from its frame. Metal frames of windows and doors are very effective transmitters of signal (as well as temperature), either those received from the glass in windows or from spaces directly. Frames need to be acoustically isolated and thermally broken. Wood frames are much better for this purpose.
One of the shortcomings of relatively new use of cold-formed metal studs for exterior walls is that they transmit sound and temperature far more than masonry, so much so that green designers recommend that they not be used despite seeming cost savings.
Metal studs in gypsum board walls are wonderful transmitters, indeed, the studs and gyp board may act as amplifiers, no matter the STC rating derived from other characteristics. Again, wood studs are preferrable, or the metal studs must be isolated by double layering and gasketing.
Wet wood is a transmitter of signal and temperature, dry wood less so.
There are synthetics and/or composities which can take the place of wood and metal studs. Not yet cheap enough to be used widely.
Now, metal nails, screws, brackets, masonry reinforcement, ties, support angles and whatnot still remain a source of signal. High-strength adhesives and isolation devices improve the resistance to transmittal.
The wondrous materials of the stealth machines may come into architecture some day, but not soon. Well, maybe the TLAs are using them in SCIFs, the super-versions.
Bamford's latest book is chock full of nightmare technology and programs for invasive methods well beyond most of healthy paranoia about incomsec.
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