I agree leeneia - to the extent that I wonder if our defensive reaction to alarm type noises (not just man-made ones) are being dulled.
Over-use of alarm type noises leads to a sense that these are no longer dangerous so over time we could possibly find that we do not react when we need to.
I'm sure the police have found this which is why they now have the multiple tone sirens with wizzes, wows, whoops and rat-a-tat-tats.
If a car alarm goes off near your house do you automatically think "Oh my goodness, someone is breaking into a car" ? In 99% of cases the only crime going on is disturbing the peace.