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Subject: Re: Amplifying weak sounds
Date: Tue, 12 Nov 2002 14:13:43 GMT
NNTP-Posting-Date: Tue, 12 Nov 2002 09:13:43 EST
Organization: Road Runner
A. Marjovi wrote:
> Dear List
> I want to build a microphone and amplifier that can amplify sounds
> from a distance. for example you can walk while talking in a 3*4
> meters room which
> has been equipped with this microphone sysytem.
> Any comment about the type of microphone and amplifier design?
There is a technique used for covert surveillance where a laser is
bounced off a window pane. Any sound in the room which vibrates the
glass will show up in the beam returned from the glass.
Another technique is to put a wire around the perimeter of the entire
room. Sound can be picked up this way, but the last I heard on the
subject, nobody knows why it works.
That said, standard electrete microphones placed at various points in
the room should be fairly effective, and far less complicated than the
methods mentioned above. The direction they are facing and the enclosure
they are placed in will impact the effectiveness greatly. You can see an
example of one design that is supposed to pick up sounds from all around
a central point by looking at a product here:
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