Adding the automatic en/disabling of the volume controls based on whether the player is actually able to send voice (i.e. do they have a device available, are they connected to the channel). Adding logic to display a mic icon for the local user instead of the volume control, so they just have the mute toggle. It still needs a mic icon.

Assets/Prefabs/UI/UserCardPanel.prefab

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Assets/Scripts/UI/LobbyUserVolumeUI.cs

 
 namespace LobbyRelaySample.UI
 {
-    // TODO: Necessary?
-    public class LobbyUserVolumeUI : UIPanelBase
+    public class LobbyUserVolumeUI : MonoBehaviour
+        [SerializeField]
+        private UIPanelBase m_volumeSliderContainer;
+        [SerializeField]
+        private UIPanelBase m_muteButtonContainer;
+        [SerializeField]
+        [Tooltip("This is shown for other players, to mute them.")]
+        private GameObject m_muteIcon;
+        [SerializeField]
+        [Tooltip("This is shown for the local player, to make it clearer that they are muting themselves.")]
+        private GameObject m_micIcon;
+        public bool IsLocalPlayer { private get; set; }
+
-            Show();
+            if (IsLocalPlayer)
+            {
+                m_volumeSliderContainer.Hide(0);
+                m_muteButtonContainer.Show();
+                m_muteIcon.SetActive(false);
+                m_micIcon.SetActive(true);
+            }
+            else
+            {
+                m_volumeSliderContainer.Show();
+                m_muteButtonContainer.Show();
+                m_muteIcon.SetActive(true);
+                m_micIcon.SetActive(false);
+            }
-            Hide();
+            m_volumeSliderContainer.Hide(0.4f);
+            m_muteButtonContainer.Hide(0.4f);
+            m_muteIcon.SetActive(true);
+            m_micIcon.SetActive(false);
-    }
-
+        /* TODO : If we can hook in the volume from a user, we can plug it in here.
+              /// <summary>
+              /// Controls the visibility of the volume rings to show activity levels of the voice channel on this user.
+              /// </summary>
+              /// <param name="normalizedVolume"></param>
+              public void OnSoundDetected(float normalizedVolume)
+              {
+                  m_voiceRings.alpha = normalizedVolume;
+              }
+              */
+    }
 }

Assets/Scripts/Vivox/VivoxSetup.cs

 
             m_loginSession.BeginLogin(m_loginSession.GetLoginToken(), SubscriptionMode.Accept, null, null, null, result =>
             {
-                // TODO: Is BeginLogin guaranteed to call this callback?
                 try
                 {
                     m_loginSession.EndLogin(result);

Assets/Scripts/Vivox/VivoxUserHandler.cs

     public class VivoxUserHandler : MonoBehaviour
     {
         [SerializeField]
-        private UI.MuteUI m_MuteUI;
-        [SerializeField]
         private UI.LobbyUserVolumeUI m_lobbyUserVolumeUI;
 
         private IChannelSession m_channelSession;
         private const int k_volumeMin = -50, k_volumeMax = 20; // From the Vivox docs, the valid range is [-50, 50] but anything above 25 risks being painfully loud.
+
+        public void Start()
+        {
+            m_lobbyUserVolumeUI.DisableVoice();
+        }
-            Account account = new Account(id);
+            // Account account = new Account(id);
-        }
-        private void FindVivoxId()
-        {
-            if (m_vivoxId != null || m_channelSession == null)
-                return;
-            foreach (var participant in m_channelSession.Participants)
+
+            // SetID might be called after we've received the IChannelSession for remote players, which would mean after OnParticipant Added. So, duplicate the VivoxID work here.
+            if (m_channelSession != null)
-                if (!participant.Key.Contains(m_id))
-                    continue;
-                m_vivoxId = participant.Key;
-                return;
+                foreach (var participant in m_channelSession.Participants)
+                {
+                    if (m_id == participant.Account.DisplayName)
+                    {
+                        m_vivoxId = participant.Key;
+                        m_lobbyUserVolumeUI.IsLocalPlayer = participant.IsSelf;
+                        m_lobbyUserVolumeUI.EnableVoice();
+                        break;
+                    }
+                }
             }
         }
 
+            m_channelSession.Participants.AfterKeyAdded += OnParticipantAdded;
+            m_channelSession.Participants.BeforeKeyRemoved += BeforeParticipantRemoved;
+            m_channelSession.Participants.AfterValueUpdated += OnParticipantValueUpdated;
+            m_channelSession.Participants.AfterKeyAdded -= OnParticipantAdded;
+            m_channelSession.Participants.BeforeKeyRemoved -= BeforeParticipantRemoved;
+            m_channelSession.Participants.AfterValueUpdated -= OnParticipantValueUpdated;
+        /// <summary>
+        /// To be called whenever a new Participant is added to the channel, using the events from Vivox's custom dictionary.
+        /// </summary>
+        private void OnParticipantAdded(object sender, KeyEventArg<string> keyEventArg)
+        {
+            var source = (VivoxUnity.IReadOnlyDictionary<string, IParticipant>)sender;
+            var participant = source[keyEventArg.Key];
+            var username = participant.Account.DisplayName;
+
+            bool isThisUser = username == m_id;
+            if (isThisUser)
+            {   m_vivoxId = keyEventArg.Key; // Since we couldn't construct the Vivox ID earlier, retrieve it here.
+                m_lobbyUserVolumeUI.IsLocalPlayer = participant.IsSelf;
+                m_lobbyUserVolumeUI.EnableVoice();
+            }
+        }
+        private void BeforeParticipantRemoved(object sender, KeyEventArg<string> keyEventArg)
+        {
+            var source = (VivoxUnity.IReadOnlyDictionary<string, IParticipant>)sender;
+            var participant = source[keyEventArg.Key];
+            var username = participant.Account.DisplayName;
+
+            bool isThisUser = username == m_id;
+            if (isThisUser)
+            {   m_lobbyUserVolumeUI.DisableVoice();
+            }
+        }
+        private void OnParticipantValueUpdated(object sender, ValueEventArg<string, IParticipant> valueEventArg)
+        {
+            var source = (VivoxUnity.IReadOnlyDictionary<string, IParticipant>)sender;
+            var participant = source[valueEventArg.Key];
+            var username = participant.Account.DisplayName;
+            string property = valueEventArg.PropertyName;
+
+            if (username == m_id)
+            {
+                if (property == "UnavailableCaptureDevice")
+                {
+                    if (participant.UnavailableCaptureDevice)
+                    {   m_lobbyUserVolumeUI.DisableVoice();
+                        participant.SetIsMuteForAll(m_vivoxId, true, null); // Note: If you add more places where a player might be globally muted, a state machine might be required for accurate logic.
+                    }
+                    else
+                    {   m_lobbyUserVolumeUI.EnableVoice();
+                        participant.SetIsMuteForAll(m_vivoxId, false, null);
+                    }
+                }
+                else if (property == "IsMutedForAll")
+                {
+                    if (participant.IsMutedForAll)
+                        m_lobbyUserVolumeUI.DisableVoice();
+                    else
+                        m_lobbyUserVolumeUI.EnableVoice();
+                }
+            }
+        }
+
-            FindVivoxId();
             if (m_channelSession == null || m_vivoxId == null) // Verify initialization, since SetId and OnChannelJoined are called at different times for local vs. remote clients.
                 return;
 
 
         public void OnMuteToggle(bool isMuted)
         {
-            FindVivoxId();
             if (m_channelSession == null || m_vivoxId == null)
                 return;
 

Assets/Scripts/UI/MuteUI.cs.meta

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Assets/Scripts/UI/MuteUI.cs

-using UnityEngine;
-
-namespace LobbyRelaySample.UI
-{
-    public class MuteUI : UIPanelBase
-    {
-        [SerializeField]
-        CanvasGroup m_voiceRings;
-
-        public void EnableVoice()
-        {
-            Show();
-        }
-
-        public void DisableVoice()
-        {
-            Hide(0.4f);
-        }
-
-        /* TODO : If we can hook in the volume from a user, we can plug it in here.
-              /// <summary>
-              /// Controls the visibility of the volume rings to show activity levels of the voice channel on this user.
-              /// </summary>
-              /// <param name="normalizedVolume"></param>
-              public void OnSoundDetected(float normalizedVolume)
-              {
-                  m_voiceRings.alpha = normalizedVolume;
-              }
-              */
-    }
-}