Update audio processing state: next_index=16

processing_audio_state.json

@@ -16,6 +16,7 @@
     "audio/week07 08 dynamic joint jiggle.wav": "processed",
     "audio/week07 07 adding dynamics to our muscle.wav": "processed",
     "audio/week07 06 dynamic meshes.wav": "processed",
-    "audio/week07 05 dynamic joints.wav": "processed"
+    "audio/week07 05 dynamic joints.wav": "processed",
+    "audio/week07 04 one way of building a muscle pt2.wav": "processing"
   }
 }