Activating a super ability has a sound, and trying to cut down trees or activate skull splitter when on cooldown also has a sound.

src/main/java/com/gmail/nossr50/util/sounds/SoundManager.java

@@ -86,6 +86,8 @@ public class SoundManager {
                 return Sound.ITEM_TRIDENT_RIPTIDE_3;
             case DEFLECT_ARROWS:
                 return Sound.ENTITY_ENDER_EYE_DEATH;
+            case TIRED:
+                return Sound.BLOCK_CONDUIT_AMBIENT;
             default:
                 return null;
         }

src/main/java/com/gmail/nossr50/util/sounds/SoundType.java

@@ -13,7 +13,8 @@ public enum SoundType {
     DEFLECT_ARROWS,
     TOOL_READY,
     ABILITY_ACTIVATED_GENERIC,
-    ABILITY_ACTIVATED_BERSERK;
+    ABILITY_ACTIVATED_BERSERK,
+    TIRED;
 
     public boolean usesCustomPitch()
     {