I have a strange fascination with sirens. They were everywhere in Toronto when I was a kid, and in University, I helped maintain the last of them when I worked at the airforce base. They are horrible, horrible things! They always go off when you don't want them to, and they don't go on when you want them. I can't imagine anyone willingly going to sirens.
The US nuclear plants are big on them, and so are these coastal areas. So, in a very modern world, what could be the alternative? Could we have electronic signs that normally sell soda pop in quiet times? Could every visitor with a cell phone register for emergency text messages? How about giant noisy fireworks? Anything but sirens!