MAKE SURE TO BACKUP ALL FILES

Extract all files to a folder then import vehicles.oac to your x64>audio>sfx>resident.rpf section on OPENIV.

Credits to flyer2359x

Sirens:
Police Cruisers: Whelen CenCom
FIB Vehicles: Federal Signal SS2000
Firetruck: D&R Intimidator
Ambulance: Mastercom B Siren, Yelp & Pierce only due to length restrictions.
Sheriff SUV: Federal Signal Touchmaster used for the Yelp tone.  Wail is unchangeable due to length restrictions.