Hi,
this may be quite bizarre, but on the road I got my hands on a 20-year-old, unmarked siren.

I am interested in approximately what voltage the supply needs to be, and what the operating current is. It is around 20 years old and comes from slovakia. Would something like a car battery be enough? Will I need to measure the resistance? Just a very quiet sound is enough to start with. The siren itself has only two cables.

 

If you know it is a siren, connect an amperimeter, cover your ears, plug to 12VDC briefly, read current, disconnect.
If it is loudspeakers, connect to any speaker output.
Can also be loudspeakers emitting siren sounds from an oscillator amplifier.