This script works for me for playing Audio & Video, and then changing to Level 1 when the video is done playing.

using UnityEngine;
using System.Collections;

public class VideoStream : MonoBehaviour {
	
	WWW wwwData;
	public string url;
	
	// Use this for initialization
	IEnumerator Start () {
		
		wwwData = new WWW(url);
		
		m = wwwData.movie;
		
		while(!m.isReadyToPlay)
			yield return null;
		
		guiTexture.texture = m;
		
		transform.localScale = new Vector3 (0,0,0);
    	transform.position = new Vector3 (0.5f,0.5f,0);
		
		Rect temp = guiTexture.pixelInset;
		
    	        temp.xMin = -m.width / 2;
   		temp.xMax = m.width / 2;
   		temp.yMin = -m.height / 2;
    	        temp.yMax = m.height / 2;
		
		guiTexture.pixelInset = temp;
			
		audio.clip = m.audioClip;

		yield return StartCoroutine(Play());
	}
	
	IEnumerator Play(){
		
		m.Play();
		audio.Play();
		
		while(current < m.duration){
			current += Time.deltaTime;		
		
			yield return null;
		}
		
		Application.LoadLevel(1);
	}
	
	MovieTexture m;
	float current;
}

I'm having same sort of problem and the answer I explore here seems to me effective. Hopefully by following these ways audio playing difficulty will be fixed. Thanks link text