But why?
Is it so people do not get complacent about the same old sound?
So they can still get a reaction out of people?
Modern emergency vehicles use electronic sound generating devices to make their "siren" sounds. There are normally several different sounds that can be generated from a single unit, and they DO change sounds to get drivers attention when operating in traffic.
They most certainly do. While fire trucks like to use that signature mechanical siren (it's called a Q siren, maybe that's who makes them or something), the variable-sound electronic sirens are used on just about everything.
They generate sounds from a slow rise-fall to a yelp or a whoop-whoop or whatever, and you're right: They change up the sounds so people will notice them and get out of their way. They also use horns and bells and whatever else makes noise.
I'm sure they replace the actual sirens themselves every so often, because sirens wear out just like everything else after a while.
A single sound can be filtered out by drivers until the vehicle gets very close, especially if anybody in the car is talking or if the radio is on. When the sound changes it is suddenly noticed. I have experienced this often on the road.
fire trucks police cars and ambulances all have several siren sounds they can use all depends on the driver and what he/she want's to use in traffic
