I can mute in Unity Player but in exported VR Android version I cant

I can't make sound to mute in exported vr version but in Unity Player it's working properly.Any thoughts? thanks using System.Collections; using System.Collections.Generic; using UnityEngine;

public class mutesound : MonoBehaviour, IGvrGazeResponder {

 //AudioSource audio;
 //public string Nameofscenes;
 float timer = 0;
 public bool isentered = false;
 float Gazeactivationtime = 2;
 public Transform target;
 public GameObject gameobject;
 public GameObject gameobejectsetactive;

 void Update () {
     if (isentered) {
         Temp ();
     }
 }
 void Temp()
 {
     timer += Time.deltaTime;
     if (timer >= Gazeactivationtime) {
         AudioListener.volume = 0.0F;
         //gameobject.SetActive (false);
         //gameobejectsetactive.SetActive (true);
         //timer = 0;
         //isentered = false;
     } 
 }
 public void OnGazeEnter()
 {
     isentered = true;
     //if (timer <= 0f) {
     //    SceneManager.LoadScene (Nameofscenes, LoadSceneMode.Single);
     //    timer = 3.00f;
     //}
 }
 public void OnGazeExit()
 {
     isentered = false;
     timer = 0;
     //    Time.deltaTime = 1;
 }
 public void OnGazeTrigger()
 {
     //isentered = true;
 }

}