Where did the multi-siren car alarm come from?

January 14, 2009 2:37 PM

Whence the multiple-siren sound series in annoying car alarms and some cheap laser-gun toys?

You know, this sound. I remember having a few toy guns with this sound before I heard it in car alarms. Actually, I think there was a popular variation including the sound of a falling bomb and explosion. Where did these sound series come from?

Is there some car alarm equivalent to You've Got Mail guy and the Yahoo yodeler?

posted by NickDouglas to technology (7 comments total)

This might be apocryphal, but my understanding is that some municipalities had laws forbidding a "continuous" alarm for longer than 1 minute (or some other brief length) and this was the alarm manufacturers' way around that.
posted by nicwolff at 2:52 PM on January 14

The microchip companies sell chips that synthesize these sounds. Not like flash memory with a sound file, but half-a-cent chips with the means to produce these sounds permanently etched in the silicon. I tried to google one up, but I just kept finding kits that included them.

As I think about the sounds that these chips produce, I think I have a theory on why they're all roughly the same: they're trivially easy sounds to electronically produce. You don't even have to record them in any way. You can make a siren using an oscillator and bandpass filter or tunable frequency multiplier. This means that the same tiny, simple synth circuitry can be reconfigured in several different ways to produce different sound effects.

I actually bet that the synth circuit itself has no more than 25 primitive components. All of which can be etched on the chip, except for the base crystal. The rest of the chip's realestate is going to be devoted to modulating the base frequency into all of those different annoying blips you hear.
posted by Netzapper at 3:25 PM on January 14

I've heard that these car alarms are actually designed so that the alarm owner can pick ONE of several electronic tones, and that default sound is a nice progression off all variations..

for example, you could, perhaps with DIP switches, choose just a nice steady AH AH AH AH sound, and leave out the Whooooooooot, Whoooooooot and the DEEEEDOOOO DEEEDOOOO.

But, of course, no one reads the directions and just leaves this default showcase-type setting.
posted by cockeyed at 4:59 PM on January 14

As for your toy gun, you're probably talking about the HK628? This was the crappy keychain/toy sfx ic of the 80's, per Netzapper's remarks.

That being said, the circuitry involved is dead simple, so many sirens similar to what you're talking about have probably been implemented several times independently.
posted by 7segment at 5:54 PM on January 14

Here's an NPR story about a woman who replaced the alarm sounds with matching bird calls:

The familiar urban "song" goes like this: 16 siren wails as an introduction, followed by 16 more, in a different pattern. Then eight descending swoops, then two long upward swoops, then what NPR's Rick Karr calls the "European ambulance" sound, like a shrill grunt. Finally, as a coda, a truly annoying staccato of warning tones.
...
But Brooklyn artist Nina Katchadourian has a novel solution. With help from the Sculpture Center in Queens, she’s taken three cars and fitted them with a new kind of alarm. Instead of those six annoying electronic tones, her alarms blare bird songs that more or less follow the same sonic pattern.
posted by ShooBoo at 7:34 PM on January 14

her alarms blare bird songs that more or less follow the same sonic pattern.

That's funny. The birds in my old neighborhood just imitated the car alarms. With 100% fidelity, until mating season when they'd start doing variations.
posted by Netzapper at 10:27 PM on January 14

Still wondering where the sounds originated, or how the series we frequently hear became the definitive series, but all this other info is fun. Maybe I'll have to dig deeper, call some manufacturers.
posted by NickDouglas at 11:28 AM on January 15