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From: William Ray Wing <wrw@mac.com>
Newsgroups: comp.lang.python
Subject: Re: Detection of a specific sound
Date: Tue, 03 Nov 2015 09:45:29 -0500
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> On Oct 25, 2015, at 8:17 PM, Montana Burr <montana.burr@gmail.com> =
wrote:
>=20
> I'm looking for a library that will allow Python to listen for the =
shriek of a smoke alarm. Once it detects this shriek, it is to notify =
someone. Ideally, specificity can be adjusted for the user's =
environment. For example, I expect to need moderate specificity as I =
live in a quiet neighborhood, but an apartment dweller might need more.
>=20
> I'm thinking of recording a smoke alarm and having the program try to =
find the recorded sound in the stream from the microphone.
>=20

I=E2=80=99ve been watching this thread and finally decided to jump in.

First off, we REALLY need to know a bit more about what you are trying =
to accomplish, in what sort of environment, and under what constraints =
(legal and otherwise).  That last bit is crucial.  Is this simply a =
heads up e-mail message to be sent or is it a way of notifying a backup =
(second tier) monitoring service.  Is it for your personal use, or do =
you expect to sell it (again crucial).  Does the computer you expect to =
run this on have a good UPS system (in a typical fire, AC power =
frequently fails early, sometimes it is the *cause* of the fire).  How =
are you going to get that notification out?  Does your network have =
battery backup?  Are you going to buy a station-service cell phone =
transmitter? If you are thinking of sending a cell phone msg, how do you =
guarantee the receiver is on?  LOTS of issues here.  Then, having said =
that, and in no particular order:

1) the sounders in most smoke alarms use over-driven pizeo-electric =
annunciators, their output has a VERY complex frequency spectrum with =
LOTS of harmonics.  Spectral analysis (combined with threshold analysis) =
MIGHT be a good way to go, but doing so in real time with Python would =
consume most, if not all the resources of the host computer;

2) You would (personal opinion), be much better off using hardwired or =
semi-hardwired detection.  There are several ways to go, including a =
detector microphone and transmitter such as is used to run a remote =
doorbell system (mount the microphone next to the smoke detector, then =
tap into the doorbell receiver box). These have adjustable sensitivity =
and would basically be a threshold detector.  Alternatively, almost all =
smoke detectors these days are designed to be chained to each other via =
three-wire (plus ground) AC wiring.  Two of the wires carry power, the =
third triggers all the detectors in the system to sound when if of them =
sound.  Don=E2=80=99t try to tap the signal wire (liability issues), but =
you could add another detector to the system which would act as your =
monitor if you tap *its* driver output.

3) Finally, how do you guarantee the computer on which the program is to =
run will be up at all times?  Does it auto-restart after a power =
failure, does the program auto-reload as part of the boot-up sequence, =
and finally, is the program going to have absolutely bullet proof error =
recovery?

-Bill





> Any help is greatly appreciated!
> --=20
> https://mail.python.org/mailman/listinfo/python-list