Effectiveness at operating distances:

Two local public agency risk management offices have evaluated the B&M Super-Chief siren in direct comparison with competing electro-mechanical and electronic sirens.  Both utilized large outdoor facilities to allow testing in realistic field conditions and used electronic sound measuring equipment.  At a 10 foot distance (and in the vehicle cab) one larger electro-mechanical siren was louder than the Super-Chief.  However, in each case at 100 feet and beyond, the B&M Super-Chief had notably greater sound levels than any competing siren.  Testers also noted that the perceived sound levels at 100 feet and beyond were noticeably higher with the Super-Chief.  The design of B&M sirens produces a lower, harsher tone than competing electro-mechanical sirens.  This sound maintains better volume at greater distances. 

The SAE standard for sound output specifies testing sirens at 3 meters (9.8 feet) in an anechoic sound test chamber.  While this establishes a baseline of sound output, it does not judge the performance of the siren at the distances necessary for a motorist to be able to respond safely to the warning.