add proper way for viewers to request mute of collision sounds by setting flag 0x80 on agent update Flags (const U8 AU_FLAGS_MUTECOLLISIONS = 0x80;). Their current method of comparing sound UUIDS is just BROKEN, even at SL.

OpenSim/Region/CoreModules/World/Sound/SoundModule.cs

@@ -215,6 +215,58 @@ namespace OpenSim.Region.CoreModules.World.Sound
             });
         }
 
+        public virtual void TriggerCollisionSound(
+            UUID soundId, UUID ownerID, UUID objectID, UUID parentID, double gain, Vector3 position, UInt64 handle)
+        {
+            float radius;
+            SceneObjectPart part;
+            ScenePresence ssp = null;
+            if (!m_scene.TryGetSceneObjectPart(objectID, out part))
+            {
+                if (!m_scene.TryGetScenePresence(ownerID, out ssp))
+                    return;
+                if (!ssp.ParcelAllowThisAvatarSounds)
+                    return;
+
+                radius = MaxDistance;
+            }
+            else
+            {
+                SceneObjectGroup grp = part.ParentGroup;
+
+                if (grp.IsAttachment)
+                {
+                    if (!m_scene.TryGetScenePresence(grp.AttachedAvatar, out ssp))
+                        return;
+
+                    if (!ssp.ParcelAllowThisAvatarSounds)
+                        return;
+
+                }
+
+                radius = (float)part.SoundRadius;
+                if (radius == 0)
+                {
+                    radius = MaxDistance;
+                    part.SoundRadius = MaxDistance;
+                }
+            }
+
+            radius *= radius;
+            m_scene.ForEachRootScenePresence(delegate (ScenePresence sp)
+            {
+                if(sp.MuteCollisions)
+                    return;
+
+                if (Vector3.DistanceSquared(sp.AbsolutePosition, position) > radius) // Max audio distance
+                    return;
+
+                sp.ControllingClient.SendTriggeredSound(soundId, ownerID,
+                        objectID, parentID, handle, position,
+                        (float)gain);
+            });
+        }
+
         public virtual void StopSound(UUID objectID)
         {
             SceneObjectPart m_host;

OpenSim/Region/Framework/Interfaces/ISoundModule.cs

@@ -67,6 +67,9 @@ namespace OpenSim.Region.Framework.Interfaces
                 UUID soundId, UUID ownerID, UUID objectID, UUID parentID,
                 double gain, Vector3 position, UInt64 handle);
 
+        void TriggerCollisionSound(
+                        UUID soundId, UUID ownerID, UUID objectID, UUID parentID,
+                        double gain, Vector3 position, UInt64 handle);
         /// <summary>
         /// Stop sounds eminating from an object.
         /// </summary>

OpenSim/Region/Framework/Scenes/CollisionSounds.cs

@@ -265,7 +265,7 @@ namespace OpenSim.Region.Framework.Scenes
 
             int thisMatScaled = thisMaterial * MaxMaterials;
 
-            //            bool doneownsound = false;
+            // bool doneownsound = false;
 
             CollisionForSoundInfo colInfo;
             uint id;

OpenSim/Region/Framework/Scenes/SceneObjectPart.cs

@@ -2916,19 +2916,19 @@ namespace OpenSim.Region.Framework.Scenes
             if (soundID.IsZero())
                 return;
 
+            int now = Util.EnvironmentTickCount();
+            if (Util.EnvironmentTickCountSubtract(now, LastColSoundSentTime) < 200)
+                return;
+
             ISoundModule soundModule = ParentGroup.Scene.RequestModuleInterface<ISoundModule>();
             if (soundModule == null)
                 return;
 
             if (volume > 1)
                 volume = 1;
-            if (volume < 0)
+            else if (volume < 0)
                 volume = 0;
 
-            int now = Util.EnvironmentTickCount();
-            if(Util.EnvironmentTickCountSubtract(now, LastColSoundSentTime) < 200)
-                return;
-
             LastColSoundSentTime = now;
 
             UUID ownerID = OwnerID;
@@ -2936,7 +2936,7 @@ namespace OpenSim.Region.Framework.Scenes
             UUID parentID = ParentGroup.UUID;
             ulong regionHandle = ParentGroup.Scene.RegionInfo.RegionHandle;
 
-            soundModule.TriggerSound(soundID, ownerID, objectID, parentID, volume, position, regionHandle);
+            soundModule.TriggerCollisionSound(soundID, ownerID, objectID, parentID, volume, position, regionHandle);
         }
 
         public void PhysicsOutOfBounds(Vector3 pos)

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -72,9 +72,10 @@ namespace OpenSim.Region.Framework.Scenes
 
     enum AgentUpdateFlags: byte
     {
-        None = 0,
-        HideTitle = 1,
-        CliAutoPilot = 2
+        None =           0,
+        HideTitle =      0x01,
+        CliAutoPilot =   0x02,
+        MuteCollisions = 0x80
     }
 
     public delegate void SendCoarseLocationsMethod(UUID scene, ScenePresence presence, List<Vector3> coarseLocations, List<UUID> avatarUUIDs);
@@ -142,7 +143,8 @@ namespace OpenSim.Region.Framework.Scenes
             }
         }
 
-        public bool HideTitle = false;
+        public bool HideTitle;
+        public bool MuteCollisions;
 
         private ScenePresenceStateMachine m_stateMachine;
 
@@ -2652,6 +2654,8 @@ namespace OpenSim.Region.Framework.Scenes
                 SendAvatarDataToAllAgents();
             }
 
+            MuteCollisions = (agentData.Flags & (byte)AgentUpdateFlags.MuteCollisions) != 0;
+
             // FIXME: This does not work as intended because the viewer only sends the lbutton down when the button
             // is first pressed, not whilst it is held down.  If this is required in the future then need to look
             // for an AGENT_CONTROL_LBUTTON_UP event and make sure to handle cases where an initial DOWN is not