something we have been trying to figure out.but you can either do 2 things .uninstall the newest Google.now update.and make sure u don't update it.or u can keep the new updated software of Google now and just download master clean lite .just installing that app and giving that app permission .fixes the Google now chime sound .we don't know why but it just does.if u uninstall clean master sadly the chime will also go away.its very weird !