Sat Mar 15, 2008 7:23 pm
The old air horn system in my town had a tank about the size of an outdoor propane tank and a gigantic compressor of unknown horsepower. Our area had frequent power failures in the winter, so it was important to have enough air for the duration of the outage. Then again, that tank powered two large horns and eight small ones.
My recommendation is to use several horns of different pitches to cover various frequencies. Many systems use horns of the same pitch, which can get lost in ambient noise. Even horns which sound a tuned musical chord can be effective as long as they do not sound too much like a train horn. Deep pitches are best to prevent this.
Signalling will work best if there is an established code for fires versus other emergencies. Sounding the horns for one long, sustained blast, will only annoy the neighbors. Remember that unlike a siren, horns reach their peak decibel output instantly. If there are homes close by, a pre-alarm might be appreciated.
Lex orandi, lex credendi, lex vivendi.