These are all sirens used in the US and what i think is the most realistic.
(There is a Q siren for firetruck :)

I was tired of trying to find all the sirens i wanted for my game, these are my favorite and i think most realistic sirens for the vehicles.

Sirens Replaced For

Ambulance-- Wail, Hi-Lo, Yelp

Firetruck (Has Q2B as secondary siren, my favorite siren ever)-- Wail, Q2B, Horn,Yelp

Police-- Wail, Yelp, Priority

Granger-- Wail, Yelp, Priority

FIB-- Wail, Priority

Generic Bullhorn

Motorcycle-- Wail, Priority