Why do police cars in the US have different siren sounds?
No real reason, other than being able to change it up to get someones attention. The three most common are the wail, the yelp, and hi/lo. The wail is a long, drawn out one, the yelp is much faster, and the hi/lo is the European style back and forth sound. We have a volunteer rescue squad in our town, they refer to the yelp as an “intersection siren”, they switch to it while approaching busy intersections, as it seems to have more of a sense of urgency. That is their policy only, I’ve never heard of a standard procedure.
