In addition to what CptLogicDev said, since you want the sound to play when the player enters an area...
You need AddEntityCollideCallback in OnStart, like this
void OnStart()
{
AddEntityCollideCallback("Player", "YOUR AREA NAME HERE", "PlaySound", true, 1);
}
void PlaySound(string &in asParent, string &in asChild, int alState)
{
PlaySoundAtEntity("", "sound file with snt", "what entity the sound plays on", i use 1 often, save the sound true or false);
}
It's all in here...
http://wiki.frictionalgames.com/hpl2/amn..._functions