This is a convert of Double Doppler's MET British siren for GTA 4. All credits for the sound files goes to them.

Install instructions

1: Export your vehicles.awc as OAC to somewhere
2: Replace the vehicles folder with the one given
3: Import vehicles.oac

Includes a wail, phaser, yelp, and hi-lo. Hi-lo replaces AMBULANCE_WARNING

I had to remove 2 sound files; The train rumbling sound, and the clown horn, as keeping them made the vehicles.awc folder over 15.75 mb, muting the in game vehicle sounds.

Enjoy!

Video showing siren: https://www.youtube.com/watch?v=aWgtFxatyCc