just wondering, why do police sirens have about 3 different sounds, and what are they used for? they have the normal wail then a really slow wail and a really funking quick warble, what are the different noises for does anyone know? any traffic cops on here?
al

Different tones for different peeps.. really high one for all the dogs driving Fiestas

...and a really high pitched wooooooohhhh!!! when they're chasing camp people

Often wondered that myself.
It does seem though that the funky tone is deployed when they want you out the way or are approaching lights etc.

How comes is it that only fire trucks have a great big horn???

Its to do with the distance the different tones travel, long wail reaches further down the road, then they switch to the shorter more intense siren when coming up to junctions, traffic lights and roundabouts as the nosie bounces off the nearby cars and buildings hopefully alerting the deaf t..s that havent heard the longer wail!!!!

Then there is the screaching noise that sounds like someone scratching a record for the, "Now im really pissed off with you move out the way" scenarios...


Hope this helps

The new BMW traffic cars have the FOG horns fitted to them like the fire trucks......

Quite effective............from what ive seen....




Hope this helps

[Edited on 9/10/08 by cashy]

The warble is a type of black noise, that unlike white noise allows the listener to very quickly identify the direction of the sound i.e. making you aware where the car is and where it's going. We use a similar type on our robots at work

I've heard some that go Nee-Naw-Nee-Naw-Pthththth-Nee-Naw- ...

Apparently the Nee-Naw bit is hard to locate; people don't know where the siren's coming from. The raspberry noise is not as audible, but very easy to locate.

Can only speak from my years in the Fire Service but basically we had different tones for different approach scenerios ie-
Certain tones are directional and make it easier to identify the direction the vehicle is coming from when approaching lights etc
Other tones work better in built up areas and others are more effective for long distance approach/ warn off, two tones were left connected alongside the electronic ones as a back up.
Also if more than one vehicle was in convoy two identical tones could cancel each other out. I cant vouch for bells as these were removed from service before I joined (but not by long!!)

As above.

All for different road conditions and speeds.

I joined the fire service after bells but I'm sure somebody will come along soon who remembers them ........come on Phil..... :-)

haha thank you kindly for the replies just interesting really never knew why they had different tones, and now i do

In the States they had a problems with Fire trucks using simple 2 tone warnings.
The noise from the fire engines own 2 tone could drown out that of another engine attending the same fire and this had led to collisions at intersections. The idea was then to interrupt the 2 tone with a completly different sound so that it could be discerned above the engines own siren.

Like all these things I am sure there was a lot of research into the different sounds, but this was one of the root causes behind the changes.

In strathclyde most pandas have the weeeeeeooooooo weeeeeoooooo and wee wee wee wee wee wee. Our traffic cars have the weeeeeooooo weeeeoooooo, wee wee wee wee, and bee baw bee baw bee baw (which never get used. The weeeeeoooo weeeeooooo is for when you are travelling at higher speeds on roads with very few junctions as it send the sound out further. The wee wee wee wee wee (otherwise known as 'yelp' is for slower driving in built up roads where there is more traffic as it sends the sound out a shorter distance but over a greater radius and is more noticeable (allegedly). Truth is the majority of people still dont see you. I think I have managed to put this post very technically, not too technically I hope?