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Re: Detection of a specific sound

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From Dennis Lee Bieber <wlfraed@ix.netcom.com>
Newsgroups comp.lang.python
Subject Re: Detection of a specific sound
Date Tue, 03 Nov 2015 09:03:14 -0500
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On Tue, 3 Nov 2015 08:50:34 +0000 (UTC), alister
<alister.nospam.ware@ntlworld.com> declaimed the following:

>Personally I would forget trying to analyse sound & see if there is any 
>way to get an input signal direct from the alarm (even if that is as 
>crude as taking a tap from the siren feed wires) 
>
>This application sounds far to critical for anything else.

	A direct line is what I'd recommend too -- but I'm going to be paranoid
today:

	If a fire did occur, and the inspectors find traces of wiring going
into what was supposed to be a stand-alone detector there is a risk that it
will be concluded that the detector had been tampered with and may not have
been functional... And that could lead to all sorts of liability problems.

	I don't know if anyone makes a model that falls between (common)
stand-alone and full monitored (tied to burglar alarm system with a service
provider responding to triggers). Something of a monitored type (hence
designed to be wired to central panel) but without the outside monitoring
agency.


	Barring that... if the detectors are all close in pitch, a PLL circuit
fed from the microphone, using the "locked" signal to indicate when the
alarm is chirping -- gives a simple on/off digital signal for the computer
(the computer may be needed to ensure the chirps are at an expected rate
and not stray whistles). Beyond that, FFT to look for spectral signature of
chirps.
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
    wlfraed@ix.netcom.com    HTTP://wlfraed.home.netcom.com/

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Thread

Re: Detection of a specific sound Michael Torrie <torriem@gmail.com> - 2015-11-02 20:49 -0700
  Re: Detection of a specific sound alister <alister.nospam.ware@ntlworld.com> - 2015-11-03 08:50 +0000
    Re: Detection of a specific sound Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-11-03 09:03 -0500
      Re: Detection of a specific sound alister <alister.nospam.ware@ntlworld.com> - 2015-11-03 14:49 +0000
    Re: Detection of a specific sound Random832 <random832@fastmail.com> - 2015-11-03 09:57 -0500

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