the computer is plugged into a surge protector thats plugged into a grounded outlet. the speakers are plugged into the same outlet as the surge protector. the speakers plug is a 2 prong and dose not have a ground prong.
and i don't know if the cable running out from the system is shielded.
however i have picked up radio stations at least once and i think i also picked up the airport by my house before
Of course the system will produce hum and buzzing if its input cables are not shielded. The system was shipped from the factory with shielded audio cables for the inputs. Use them.