I am not an America and not familia with your police cars but at a guess could it mean it wasnt a super emergency. Perhaps they want to get through the traffic but not as urgently ? In the UK our police only use the blue strobe if it a non emergecy call.

If an insane person had escaped it should be more urgent ?

I have just found an article on police car sirens you might find of interest (link)

Fog warning siren over water?

Or a test for a civil defence siren ( sounds something like the air raid sirens in WW2 films).

Or some child with a new toy. That will stop soon as an older relative consigns it to the dustbin or the child to its room!

It sounds to me like an air raid siren. But that is not likely unless you live in a war zone.

Maybe some kind of natural disaster?

Just a police car driving really slowly

yea

Ok well I'm at my house and every few minutes I here a really slow siren that lasts for a looong time ... What does that mean ... My only reference is from movies when it means an insane person has escaped ... Lol please help