You do realise there's an option for that right... it's like not that hard to find it...
The sound of octavia ability have a max range, if you are too far or there's a door between you and the mallet or resonator it mute their sound.
If you dont have the skin and syandana equipped the arm wont show up if you only have for exemple the syandana (as the arms come from it) and yes they only show up from casting (which is pmuch only for 1s)