Re: Detect sound of breaking glass


"Peter K." <p.kootsookos@xxxxxxxxxx> wrote in message
news:1140538375.679567.261220@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Noway2 wrote:

Thats a really good question and I too woudl really like to know how
these devices work. I have a number of them installled in my home
alarm system and I have found that they are sensitve to vibration.
They are also supposed to be tuned to the sound of glass breaking and
that is even supposed to have been refined to particular types of glass
(window / door) so that if you drop something on the floor it doesn't
set off the alarm. As much as I would like to try them out, I am
certainly not going to break a door or window to prove it :)

You can also try playing a .wav file reasonably loudly close to one of
the sensors. That should set it off, also, provided the .wav was
really recorded from breaking glass. :-)

Way back in the dim and distant past the acoustic detectors for smashed
windows just used to look to see if there was a lot of high frequency
component in the sound ( often triggering with an edge detector) they were
horribly unreliable though and would go-off if people rubbed a ring over the
outside of the shop window or parked their bike there and it slipped a bit.,
even a zipper tag on a coat blowing against the window or some
rubbernecker's spectacle frame clattering on it was enough to set them off
on maximum sensitivity and if you set the sensitivity lower you could often
smash large chunks out without setting them off. I expect things have got a
bit more sophisticated now but I really recommend that whatever you finally
settle on you check out sensitivity to 'normal' noises you can get out of
unbroken windows.

Best of Luck - Mike





.

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