My immediate response is that putting some tiny rings of metal on a window somewhere in a room will not somehow absorb and decrease the amount of EM in a room b

My immediate response is that putting some tiny rings of metal on a window somewhere in a room will not somehow absorb and decrease the amount of EM in a room by any measurable amount, harmful or otherwise. Additionally, the amount of energy that could be harvested this way is a few orders of magnitude less than what would be required to oscillate a window with enough force to cancel sound.