this video justices the loudness of american fire alarms

[german_siren]

http://www.youtube.com/watch?v=z8ZQ9fGqBP0 the discription says he lives about 1/4 Mile away! and you can hear still the alarm! awesome.

[lilsirenguy]

Simplex TrueAlert alarms. Crazy loud!

[Daniel]

Most American schools now use an electronic tone instead of a mechanical bell, and some of those can be heard a long distance as well. I don't know of any American schools using the traditional four-note chime in most German schools, however.

[german_siren]

yeah they use the piezo principle like ther sounderws or audio singaling devises