Emanation Shielding with Music

[John Young]

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.

__________

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." 

__________

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.