[mirotalksfu] - improve AudioLevelObservation

public/js/RoomClient.js

@@ -2816,7 +2816,7 @@ class RoomClient {
             if (consumerAudioBtn) consumerAudioBtn.style.color = audioColor;
             if (pbProducer) pbProducer.style.height = '0%';
             if (pbConsumer) pbConsumer.style.height = '0%';
-        }, 4000);
+        }, 2000);
     }
 
     // ####################################################