How can I resolve ground loop Issues (Hum or Buzzing Noises)?
Ground loop result from devices that introduce an electric potential to the ground connection:
1. Peripheral devices connected to your computer.
2. Using multiple power outlets.
3. Power inter-connected equipment from different AC outlets is likely to create a ground loop
4. Wifi routers - Poorly shielded cables - Powerline ethernet adapters - New hardware in the computers - Certain software running - Wireless mouse ...etc.
To sum up, ground noise and electrical interference happen at an electrical level. Make sure to exclude the above factors.