A Klaxon™ (yes, it’s a trademark) is an “electromagnetic horn or alerting device.” Car horns are a kind of klaxon. They have a distinctive “ahooga” sound (thus saith Wikipedia), which The Blogger’s Best Friend™ tells us was a product of the way the thing worked. Either a human or electric motor turned a cogwheel that hit a riveted-down diaphragm attached to a horn, which amplified the sound and directed it outward.
You see a hand-cranked Klaxon during the opening credits of the TV show Baa Baa Black Sheep (later syndicated as Black Sheep Squadron), which ran from 1976-1978 and starred Robert Conrad as Major Gregory “Pappy” Boyington, USMC.
The Klaxon has been pretty much replaced by electronic alarms, but the “ahooga” sound remains. Here are some samples.
Here’s an air raid siren, also used for tornadoes.
I heard this a lot in my old neighborhood.
And one more…