How to activate them? I'm using customized sirens for a long time and just noticed an AI Ambulance using them.How do you turn it on?

Well if they're using it, it must be one of your 3 tones. Hold G on your keyboard, or Click+Hold your left stick if you're using a 360 controller.

The ambulances have a different second siren than the police cars.

Not that I've noticed.

Not that I've noticed.

They do though.

What does it sound like?

They do though.

break and cj24 are right

What does it sound like?

Download SparkIV, go to sfx/resident.rpf/horns.ivaud - There is a file called Ambulance_Warning.wav - It's different from Police_Warning (which is the priority siren). The Ambulances in GTA IV have their own priority sounds, for some reason, I also recall firetrucks having a file for their own aswell. I wonder why rockstar did that, I mean, they applied the same siren to every service; they could have aswell given every service it's own siren files and then made a proper EQ2B.

I'd be hesitant to call the Rockstar North developers lazy, but...

Damn,son! I didn't know that too.Actually,I'm not into that Paramedics or firefighters thingy so I never drove the Ambulance and/or the firetruck in IV.I'll get on and see.

Really? You guys never noticed that?

I discovered that way back in 2009 when I first got the game.

Yeah,no doubt,...papi.xD