This is a Fire siren.The siren sound is up above

(install)
(open open IV and go to x64 audio sfx resdint.rpf and go to the vehicles folder and export it
to open format and export it to a folder.next open the folder and go the the vehicles folder next take
fire horn and drop it in there,next drop the wail,next drop the yelp,now go to open iv x64 audio sfx resdint.rpf
and inport open format (ENJOY)

Thats all for now.
I have done my best to make a good sounding fire siren Hope this helps you out (ENJOY)