Is EMI noise in electrical system inaudible?

I think you might be wrong despite your level of enthusiasm.

Possibly.  Kind of depends, but it's rare. My approach is to stick to inexpensive solutions, but here's what I do:

• Use fully shielded interconnects
• Use shielded power cable for analog parts. These can be pretty affordable
• Use iFi power supplies where they matter, on my DAC and streamer to minimize the generation of AC noise.
• Use a power conditioner that starts working down in the audible range.  That includes those Furman with LiFT and SMP features and TrippLite Isobar. 
• Try to keep my network devices (switches, routers, etc) away from my audio, both physically and the power supplies out of the same clean zone.

+100 Jason!

+200 @jasonbourne52!