If you want the sound to be played every time the trigger is touched then use a trigger_multiple or If you only want it to play once, then trigger_once with a ambient generic (give a name to the ambient generic).
Outputs : OnTrigger > ambient generic name > PlaySound
On the ambient generic you might have to tick "Is not looped" in the flags tab depending if you're using a MP3 or WAV.
The door should have an area portal in it. Link it to the door so that when the door is closed, the areaportal is closed. This will seal off the visleafs and cut out the light completely. either that or make the prop a brush door, or have shadows.