How to play Audio Once if enemy has enterd a trigger

Hi Guys. trying to make my zombie scream if he enters my trigger. This is the script i have came up with

var target : Collider;
private var triggered : boolean = false;


function OnTriggerEnter(collision : Collider)
{
 if (collision !=target)
 {
 return;
 }

triggered = true; 
audio.Play();
}

How do i tell it what audio to play. My sound is called “ZombieScream”

also my zombie is taged Enemy if thats any help.

You want to use audio.PlayOneShot(clip : AudioClip);

http://docs.unity3d.com/Documentation/ScriptReference/AudioSource.PlayOneShot.html