You need an occiliscope to see the dirt i.e. what looks like little lines
going up and down along the AC arc making the sign wave look thick and scribbly because they are very small voltages .
These lines can be in the mega Hz range and down to the hearing range of 20,000 Hz and below and.
I do know that the creator of the dirtiest in-house electricity are motors ,
the refrigerator , the washer and dryer and dirtiest of all the furnace fan moter and the heat pump . Flourecent lights are a close second .
Most of my AC conditioning is passive , PS audio noise harvesters ,
Greenwave noise filters and everything that is plugged in goes through
a Tripp-lite ultra surge/filter outlet box .
oregonpapa said it best ,
it's noise that you didn't know it's there until it's gone !