How to improve voice quality in Photon Voice?

The following code does establish Photon Voice networking but the quality of voice is not good. Plus there is a lot of noise. How do I make sure that there is minimal noise? Furthermore how do I pause and unpause sending of voice to the other users?

using UnityEngine;
using System.Collections;
using Photon;
public class NetworkManager : Photon.PunBehaviour
    private GameObject studymaterial;
    void Start()
        PhotonNetwork.automaticallySyncScene = true;
        PhotonNetwork.logLevel = PhotonLogLevel.Full;
        studymaterial = null;

    void OnGUI()
    public override void OnJoinedLobby()
        RoomOptions roomOptions = new RoomOptions() { isVisible = true, maxPlayers = 18 };
        PhotonNetwork.JoinOrCreateRoom("Class", roomOptions, TypedLobby.Default);
    public override void OnJoinedRoom()
        PhotonNetwork.Instantiate("User", new Vector3(0, 1, 0), Quaternion.identity, 0);
       // studymaterial = PhotonNetwork.Instantiate("Heart3D", new Vector3(2, 1, 0), Quaternion.identity, 0);



in photon voice example you see object Voice

you should able to make your own setting and less the noise as possible.

how do I pause and unpause sending of voice to the other users?

and all you want also including in the demo scene there a complete UI setting for player