I am currently enrolled in a driver / operator class for my fire department and a statement that was written in our text books has been bothering me. " If a fire apparatus is traveling at 40 miles per hour the siren can be heard at a distance of 300ft. However, if a fire apparatus is traveling at 60 miles per hour the siren can only be heard from a distance of 12 ft." I have always been told that the faster an Emergency vehicle goes the less effective the sirens become... to me that is questionable and this drastic falling off of audible sound is almost unbelievable, especially at such low speeds. I'm not sure exactly how loud the siren is that the book is referencing only that this statement is unrealistic but hey i could be wrong and probably am. If anyone could explain to me how they got this and if they are even right i would greatly appreciate it. I have looked everywhere and can not find any relation to speed, sound, and audibility. This quotation is taken from a California State Driver Operator Handbook that is a required read to become state certified.