Sirens are only effective in certain locations such as Hawaii or the coast (tsunamis) or parts of the mid-west (Tornado alley) where everybody knows what they mean.

So if I hear a siren in MP what does that mean? Even if they have variable tones, what does each one mean? There's a HUGE continual educational component associated with their presence not only for residents but also for visitors. Even if I hear one and understand, what do I do?

Even ones that have the ability to announce -- who's paying attention, who has ear buds in, who's playing music, who's indoors with the windows shut and the TV on.

Only useful in specific locations -- not worth the investment. There are other more effective ones.