Re: Glass breaks, thunderstorms and HA (was Re: Help with 7 Circuit Project?)

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Marc F Hult" <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message

<stuff snipped>

>>It would be interesting to mount microphones on all four
>>corners of the roof and feed them into a digital multi-track
>>recorder and the superimpose the wave forms to see if they
>>correlated with my own estimates of the direction.
>
> That's an interesting idea too. Sound travels ~1150 feet/second so (eg) a
20
> hz wave is about 56 long. So sounds from the same source reaching
locations
> ~28 feet apart cancel. So as you suggest, I'd think you'd still need to
> identify the entire 'signature' and not just compare instantaneous
> amplitude.

That's certainly a consideration for building a 4 input comparator circuit.
If I designed the circuit so that a capacitor was charged by the
microphones' output for 1/x seconds wouldn't that overcome the out-of-phase
problem?  It would enable me to "accumulate" the thunderclaps.

> Which is what I was referring to, namely,  using software to identify a
> characteristic sound from a single microphone. Savoy's Cyberhouse's
> Listen.exe can do this.

Yes, I understand that.  It works like DragonDictate, except that instead of
putting a word on the screen in response to a "sound match" Savoy's program
allows the controller to take an action.  I assume, based on my experience
with Dragon, that it's not 100% reliable without training.

> There are also commercial, scientific, and freeware
> programs to do this that might be adapted. Google on
> "sound recognition"

I think I'm going to spend a little more time modeling the problem.  I want
to detect thunder mainly to prevent false alarms from my glass break
detectors.  Since, as you point out, the audio "signature" of thunder is
highly variable, it seems it would be pretty futile trying to make a sound
match.  It would also require PC horsepower, and I'd like to see if a very
simple hardwired circuit could also do the trick.  I think what you
suggested earlier in the thread (some op-amps and gates) would work very
nicely simply based on the amplitude of the sound.  It might also be
necessary to filter out all but the lowest frequency sounds and, as you
pointed out, compensate for possible cancellation of the sound waves.

> http://www.merl.com/projects/SoundRecognition/

> As I noted previously, the sound of lightning-induced thunder is complex
and
> variable.
>
> See: http://freesound.iua.upf.edu/tagsViewSingle.php?id=951

Yes, agreed.  Sound pattern matching is not a good solution for a number of
reasons.  But four microphones, a few IC's and stuff from my junkbox might
work.  I have to decide whether to amplify the signals close to the
microphone (probably best since it would be more likely to compensate for
difference in output level due to line length) and how to test the circuit.

--
Bobby G.