Most Irritating Sound from a Piezo

[Cosmic Software]

I am in need of a sound generated by a small piezo sounder that makes you cringe when you hear it.

It does not need to be loud, but it must be uncomfortable to listen to as it will be used as an output from a tamper sensor in a security system.

I have already tried to use ascending and descending tones, and even random sequences using the SOUND command, but I have not come up with anything that is suitable.

I could use the SOUND or TUNE command if anyone has some ideas.

 

[andrew_qld]

I don't know you'll get enough volume out if a plain pizeo driven with a picaxe- I'd use an off the shelf pizeo "siren" that just needs +12v applied to it and use a relay or transistor to drive it from the picaxe. Some of these things have 118dBA output!
I have used off the shelf pizeo sirens from Jaycar and Dick Smith Elecronics in Oz, but I'm sure you could find something locally.

Cheers,
Andrew

 

[marcos.placona]

You can even get one from a smoke detector. They are quite annoying, and quite cheap too.

Just remember that one sound can be quite annoying to one, but simply a loud sound to others.

My wife will be really annoyed when I play very low frequency sounds (those that normally can just be heard by kids). On the other hand, I can't even hear them.

BTW, my wife is not a kid, just so you know

 

[Grant Fleming]

I don't know you'll get enough volume... Some of these things have 118dBA output!
I have used off the shelf pizeo sirens from Jaycar and Dick Smith Elecronics in Oz, but I'm sure you could find something locally.

This is the kind of thing you are looking for, NOT!
It surely would be 'irritating' anyway!

Cheers,
Grant

 

[manuka]

Thought-play some offensive "music"! If your target audience is youthful, the likes of Frank Sinatra singing "New York-New York" can make even the most hardened rascal scamper.

I'd a teaching mate who used this in his "after school club" detentions, & kids would do almost ANYTHING to avoid the audible torture. Youthful ears can't stomach finger nails scratched on chalkboards either.

 

[Dippy]

I've only heard a couple of 'tamper' noises from Alarm Panels. They were loudish 2-tone beep-BEEP type things. That really gets on your nerves after a few minutes.

You'd never get enough volume from a direct powered PCB mount peeper assuming the whole thing is in some kind of box.

As suggested above a driven device is the answer. I think the Big Boys tend towards 'ALERT' rather than 'ANNOY'.

A voice synthesiser shouting "My PICAXE is broken after I connected it to 12Volts" is quite annoying. Trouble is the cheap synths may give the impression that Stephen Hawking is in the control panel.

PS. Sorry, I can't stand Sinatra either.. nothing personal. Knives cutting on plates and my Brother In Law eating are also offensive.

 

[kevrus]

Tom Jones music got rid of the aliens in the movie 'Mars Attacks'...seriously though, maybe an amplified white noise generator would suffice?

 

[bgrabowski]

Try this.

'Sound Pattern
'Piezo sounder connected to output 6
'
for w0 = 1 to 50
random w1 'generate next random number
b4 = w1 / 595 + 16 'calculate a pseudo-random sound frequency
sound 6,(b4,5)
next w0

 

[Michael 2727]

The 2 tone internal sirens that security companies use will almost knock you
off a ladder (when your mongrel off-sider tech plays GOTCHA! ) at a meter away.

They are white and look much like a smoke alarm or Top Hat shaped.

 

[boriz]

Crazy frog song. Or anything by Aqua.

 

[Cosmic Software]

Thank you for so many great ideas in a short space of time. The best idea is probably one that I had overlooked - a smoke alarm. I have one or two old ones lying around, so I will give it a go.

Does anyone know whether or not the siren is generated by the piezo or the onboard circuitry?

 

[Michael 2727]

Many smoke alarms have a 3 stage piezo element, the extra part is
probably used for feedback and resonance to obtain the loudest
noise from that particular element.
The third connection is quite often a thin (insulated) strip or spot on the disk.
Smoke alarm chips are detector and alarm driver all in 1.
They use a very high gain op amp/comparator to detect the smoke when
a radioactive particle hits it.

You could probably fool the comparator, but they are a very finely tuned circuit
and results could vary.

 

[Dippy]

I don't know whether they're all the same Cosmic.
If you have a couple lying around why not have a look?

Cosmic, the piezo is the transducer. It don't generate nuffin! It is driven like a loudspeaker and to get biggest noise it is driven at or near resonance.

 

[slimplynth]

No one pays attention to burglar alarms anymore

**slimplynth gets started on the... picaxe - olfactorynator**

Who needs a siren? Everyone expects a siren The smell of either vomit or babies nappies would put me off tampering.

Also in the pipeline: "Organic anti-climb paint"

 

[hippy]

Perhaps the most annoying thing I know is anything which runs on a regular two-tone beat - de da de da de da de da - which brings back the happy days of head banging ( try resisting ) and then throw a glitch in to destroy the rhythm.

 

[marcos.placona]

I think the best concept today is to use some flame-throwers! Have you guys heard about the anti-theft device that throws a flame from underneath the car when someone tries to break into it?

It'd look like this:

 

[Dippy]

Yes, I reckon your car spitting fire in the garage would certainly let you know that someone was tampering with your alarm system.
Dear oh dear...

Cosmic, if you don't want to build a driver circuit then places like Farnell are bursting with beepers.
The last panel I looked inside years ago used a small weatherproof loudspeaker as the 'internal' sounder. It did a loud 2 tone daa-diii-daa for tamper.
Piezos are not very loud and need to be driven pretty hard and at resonance. The plastic housings that are used provided the resonant cavity.

They aren't expensive and could save days/weeks of faffing about.

 

[Joeroddis]

If you were using the fire alarm, couldn't you just remove the sensor, then to set the siren off, short the 'test' button with something like a solid state relay driven by the picaxe?

 

[boriz]

This is how those personal screamer alarms boost the volume: A coil connected to the +V at one end and to the +piezo wire at the other. The –piezo wire goes to ground. A transistor, switched at the resonant frequency, with it’s emitter to ground and it’s collector connected to the piezo end of the coil.

The transistor turns on, it grounds one end of the coil, then when it turns off, the back-emf swings the voltage across the piezo up to many times the +V supply. That’s how they get such a large volume from a PP3.

 

[Michael 2727]

Look at Tank Circuit -
http://en.wikipedia.org/wiki/LC_circuit
You really need an L C Meter for this sort of tinkering.
Or you can wind an inductor turn by turn until you hit the resonant,
may take a few weeks/months/years though.

If you know the ?? µF value of the piezo element you can find plenty of
L C Calculators on the web to find the inductor needed or close to it.
( a piezo is basically a capacitor )

This circuit rings like a tuning fork so an exactly timed short pulse
every few cycles will keep the sound going, saves power, varies the amplitude also.
A piezo element in a resonant tuned cavity will also increase the SPL, as prevoiusly
mentioned.

Much cheaper to get an off the shelf siren though