Re: Speech sensors?

[brian whatcott <inet@intellisys.net>]

Margaret,
I have seen internet discussion of the method.
 There is some doubt in my mind as to whether success depends on
a perpendicular view of a single-glazed glass pane, or if
audio can also be extracted from oblique laser views of windows.

What is certainly well-established is an Eastern Bloc substitution 
at the height of the cold-war for a US wall emblem mounted on the
wall of a secure room.
 This provided a passive microwave cavity with a flexible diaphragm
and a little monopole antenna.
 When illuminated by an external microwave beam, a return signal 
was modulated by any sound available in the room. 
 This illustrates the general principle.

Brian

At 22:36 12/26/97 +1100, you wrote:
> Does anyone out there more knowledgable than me (and that's not hard) 
> know if the following 
> technique is for real or is an urban myth: that industrial-espionage type 
> sensors exit which can reconstruct an internal conversation from the 
> remotely-sensed vibrations of a room window?
> If it is genuine, how is it done in practice?
> Cheers and Christmas Greetings to all
> Margaret Mazzolini
brian whatcott <inet@intellisys.net>
Altus OK