Add autoMuteThreshold

app/src/reducers/settings.js

@@ -20,6 +20,7 @@ const initialState =
 	notificationSounds  : true,
 	buttonControlBar    : window.config.buttonControlBar || false,
 	drawerOverlayed     : window.config.drawerOverlayed || true,
+	autoMuteThreshold   : window.config.autoMuteThreshold || 4,
 	...window.config.defaultAudio
 };