Development topic: http://gtaforums.com/topic/779568-

Introduction:
In GTA III, car alarms have a distinct alarm sound but in GTA: Vice City car alarms are simply repeated horns of the car. This mod recreates GTA III's car alarms in Vice City. See the Settings section below if you want to customize the pitch of the alarm of any cars.

In addition, when thunder is occurring, there is a chance that it will set off all car alarms for three seconds. The louder the thunder, the higher the chance. Debug mode can be toggled by typing "THUNDER". When enabled, the screen displays text with four values that are used to determine the trigger to set off car alarms during a thunderstorm. The values are the game time when thunder occurs, the lightning type, random number generator, and random number limit for the lightning type.

This mod utilizes CLEO Library for Vice City.

Thanks to Victor_Knight for suggesting thunder-triggered alarms and Mr. Jago for suggesting using GTA 2's car alarm sound.

Installation:
* Download the mod (click the Download Mod button)
* Download LithJoe's Audio Editor at http://www.gtagaming.com/downloads/gta-vice-city/tools/573.
* In your Audio folder, make sure to remove the read-only option on sfx.SDT and sfx.RAW.
* Run the editor and open sfx.SDT. Find sfx00052 and replace it with the audio supplied in the download.
* Download CLEO for Vice City at http://cleo.li/.
* From the CLEO download, copy VC.CLEO.asi into Vice City's folder.
* If CLEO.asi already exists in the folder, you must delete that file.
* From this mod download, place the CLEO folder containing SEAlarm.cs and SEAlarm.dat into Vice City's folder.
This mod has been tested only on VC v.1.00 US. Please post any troubles you have with installation. This is my first mod release that involves editing the audio file.

Settings:
The SEAlarm.dat file is a plain text file allowing you to change the pitch of the alarm for any vehicles. The file already contains the default pitch values from GTA III. Each line contains the vehicle's model index, which can be referenced from default.ide, and the pitch of the alarm. Vehicles that do not appear in the file will use the default pitch from the game. Vehicles that have a siren do not have an alarm so the pitch value changes the pitch of the siren instead.

Locations:
These are some of the locations of alarmed cars in the original game.
* Admiral at Diaz's Mansion/Vercetti Estate
* Banshee behind the Washington Beach Pay n Spray
* Infernus in North Point Mall
* Several random cars, four along Ocean Drive

Videos: