You've heard one. The Grover Emergency Stuttertone horns have been used by allmost every fire truck for years. The truck on this discussion has one. (or a pair). They have a different diaphram that makes a raspy hong. The quick hong is the operator of the siren. Only difference is the sweet raspy dual tone noise it makes. Check out this link and see for yourself: http://www.groverairhorns.com/Sounds/soundstruck.html
Any way..........
Let's say you have to approach an intersection on the other side of the median. You want the Q and horns so that people that may be turning your way will hear you comming, not the people directly in front of you.
I would love to go Q-ing in a winter wounderland, the sound realy carries in the cold!!
Even at low RPM's that q siren carries like mad. I would think you would prefer the wooop of an electronic to the safety and added protection of a Q.
Apparently the cost IS justified, almost every truck has both electronic and a Q in my city.