They sound that way to be unique and attention-getting. They have to cut through the background noise of 21st century life.
Here's a (totally unsafe!) demo from the 80's of why sirens sound the way they do. Do not attempt at home.
Here's a (totally unsafe!) demo from the 80's of why sirens sound the way they do. Do not attempt at home.
This fire alarm sounder has 32 possible sounds: https://www.youtube.com/watch?v=9os5EtDiVC4
The first is the default fire alarm noise in Britain, probably what I've heard most often.
I heard "LF Buzz" (2:32) in a nightclub, where it cut through the music. (I remember it as even more "yucky", maybe there were multiple sounders in the room.)