If you want to do it with straight code, I think Resources.Load will do what you need:
Note that your sounds would have to be stored in the Resources folder.
But if you don’t mine assigning it once, you could create an empty GameObject, name it DoorSlide, attach an audio source and assign your doorSlide sound to it.
Then in your other scripts, access it this way:
var doorOpenSound : AudioSource;
doorOpenSound = GameObject.Find("DoorSlide").GetComponent(AudioSource);