The health and balance of the blood that runs through our bodies are critical to how we function, and it is the same for the electrical health of your system. Starting at the breaker box in your home and carrying right through to the speaker drivers, what makes things work and transfers the signal, even the signal itself, is electricity.
The AC power is a "live" component, carrying noise created outside and within your audio system. The audio components themselves all put some noise back into the power line. At the same time, all the other electrical components in our lives freely contribute noise, from refrigerators or AC units polluting the ground to cellphones and computer networks broadcasting RFI. Each type of electrically generated "problem" will cause some electrical or mechanical noise that pollutes your system's signal. It's all noise, not a part of the music, and it all needs to go. Several steps can be taken to reduce the noise on your AC line, and we will go over those before I visit your home.