The "Clapper"

[nbk2000]

The "Clapper" is a device you plug into electrical outlets, then plug your appliance into, so that you can clap you hands and turn it on and opff.

I had the idea of using one as a gunshot detector inside of buildings so that, in case of armed invaders taking shots at you, the "Clapper" would switch on your defenses automatically, or the "Valhalla" defense.

Does anyone here have a clapper that they can test by putting up to a speaker playing a gunshot sound file?

I got the idea while watching a video of SWAT piggies in a shoot-house with their MP5s, and hearing the 3 shot burst in slow-mo. Reminded me of the 3 claps in the "Clapper" commercial.

[2,4,6-TNP]

The clapper may also be used as a trigger for a bomb. I can think of many ways this could be used with precision to detonate an explosive device at an exact time or as a result of various mechanical actions.

[nbk2000]

I'm just interested in finding out if it can work as a gun-shot detector without having to buy and test one myself. ;)

[mongo blongo]

I think it should work:
One of the most basic sound activated switch can be made using a mic, operational amp chip, flip flop and a relay (IIRC). A resistor must be used between the mic and the op amp (or maybe between pin 1-8 on the op amp) to change the trigger threshold onto the flip flop.
On a clap trigger, I think it is the same setup but using 2 flip flops. One of them being controlled by a 555IC timing chip (or other). The first clap changes the state of the first flip flop and another clap changes the state of the other flip flop thus activating the relay.
Because the first flip flop is limited by the set time in the 555 chip, it will change back to normal state after this time (eg 2 seconds). If there is not two claps within 2 seconds, the second flip flop will not change state. This prevents false triggering.
As to the actual sound triggering the setup, this can be any sound that is louder than the trigger threshold set by the resistor.
I should think that the commercial clap switches work on much the same principal so I can see no reason why any loud noise spike like a gun-shot would not work.

Edit: Here are two schematics out of many available on the net I found:

http://www.electronic-circuits-diagrams.com/remotecontrolsimages/remotecontrolsckt4.shtml

http://www.electronicsforu.com/EFYLinux/circuit/may2003/ci4-clap.pdf

[tiac03]

It should work, but there is too much room for error in a toy like that, anything that remotely sounds like clapping would set it off. (which is also why TNP shouldn't attempt to hook one up to anything that can exterminate him while he is setting it up)

So I assume that although it would work, there would be too many false alarms to make it anywhere near reliable.

[nbk2000]

Irony would be it setting off the 'self-destruct' when a Clapper ad came on the telly. :p

Obviously it would be a simple expedient, like in a meet somewhere with people you don't trust, and you want something to cover your ass with.

If it was to be a permanent installation, I'd have something custom made that would discriminate gunshots from other sounds by things like volume, pulse duration, frequency range, etc.

[Silentnite]

What about something like a voice recognition for your computer? You can get cables to send out a signal at a preset word or command. It wouldn't be that hard to write some code for it either.

Slightly OT but I heard that they're implementing something like this in L.A.? Sensors throught the neigborhoods and using computers to triangulate the origination of the gunshot.

[Valinomycin]

voice recognition is really damn hard to do. I've made several attempts and it never worked :( . I personally think its nearly impossible for non genious or owner of a big software company. (my systems sometimes worked for single letters under perfect circumstances)

[Silentnite]

I've had good luck with AT&T's VR engine. You just need to speak clearly. Or as my Speech Therapy teacher once said "Enunciate". Only problem is I don't have any experiance as far as whether or not there are non-english recognition's available. What about having one of those Self-defense whistles where you pull the tab, and that could be coded into the comp, or even use that as the clapper set-off, so long as you put in a higher resistor, you could actually make that permanent.
So long as you don't like tea:)

[Jacks Complete]

This will work, and the obvious way to threshold it is on volume, using a two or more microphone input.

Put one microphone on one side, and the other on the other side. Both microphones have to get above the threshold before trigger, so only really loud things will reach threshold, and a fairly loud event right next to one microphone (even tapping the mike) won't cause an unexpected issue.

Unless you are expecting someone with a moderator/silenced subsonic pistol, the extreme pressure levels from the gunshot(s) inside a small room should be quite easy to trigger on. Having done a little CQB, and shot in a lot of ranges, indoor ranges are hard on the ears even with subsonic .22 rifles, whereas outdoors they are quite quiet, as the sound doesn't echo back from the walls.

I wouldn't want to wire explosives to anything like this, but then nor would I want to try to trigger off the three round burst, the frequency signature, or anything else that is that variable - the police might use a single shot from a shotgun (130dB+, even more deafening indoors!) or an MP5 (3 shot burst?) or just a sidearm (9mm Glock or .45 1911?)

Don't forget a manual panic button as well.

With three or more sound sensors, you could have a targetting system triangulate on the noise, which could be interesting.

[nbk2000]

A lot of the SWAT pork are getting silencers on their weapons nowadays.

They say it's for "hearing protection", which I suppose it can be, but it's really just a tool for the assassins in black to quietly murder their victims without traumatizing the nearby sheeple.

That's a good idea of using two mics to average the sound input. It wouldn't be difficult in my case since I live silently, so any noise louder than a cough or a fart could be used to trigger the security.

[xyz]

The other advantage of suppressors is that they make it much more difficult (if not impossible) to locate the shooter from firing signiature (smoke/dust in daytime and muzzle flash at night).

That's why the US marine sniper teams use suppressed M16s for night sniping (the observer carries it during the day). The bullet is supersonic and still makes a hell of a racket, but the targets have no idea where the shots are coming from. Using a standard .308 sniper rifle at night will make enough muzzle flash to give you away, and since night scopes are limited to ranges of less than 300m, there is no real disadvantage to using the .223 cartridge.

This is probably even more pronounced in the situations faced by police snipers/marksmen due to the much shorter ranges involved.

[Jacks Complete]

I read somewhere (on here?) that the IR signature from a supressed rifle was very much larger than the one from an unsupressed. Apparently, the flash is bright and visible, but gives little info to the naked eye, and is likely to be missed by NVG unless in the field of view. Since these are quite narrow, you get away with it. With a supressor or brake, you get a much smaller flash from the muzzle that can be seen by the naked eye, but the glow from the IR lingers for some seconds. (Hot things cool very much faster than cold things)

You could easily triangulate off the sensors for position, and, indeed, if you wrote and wired a few of these sensors indoors, there is no reason a weatherproof version couldn't be placed about the outside, allowing for a strong passive detector net. The position and range settings could be tuned to ignore anything within the building with good accuracy, but to alert subtly if an outside event (or two to cut falsing) were detected. A good sound card with multiple inputs would not likely be enough, though.