SectorSound
From ZDoom Wiki
void SectorSound(str sound, int volume);
Usage
Plays a sound in the sector that the line the script is attached to faces. This is a point sound, so anyone far away will not hear it as loudly. Volume is an integer range from 0 to 127 with 127 being full volume and 0 being muted.
Examples
This script generates a creaking sound when walking over a linedef into a sector.
Script 1 (void)
{
SectorSound("world/creak1", 127);
}
To make this all work, be sure you've got your linedef Action Special set to 80 (ACS Execute), the Argument pointed to the correct script number, and Activation Trigger set to Player Crosses Line.

