Actually RF and EMI can and do have impact on audio components. Human hearing may be limited to 20k...but your pre-amp, power amp, and the audio sections of cd players, tape decks, etc. are not as limited as human hearing..and if RF is introduced in any part of the audio chain..components can be affected as they either expend efforts to amplify/pass along these higher freq's...or worse intermodulate them with the audio signal. So, the problem with RF is not a wire problem..it is a system wide problem that wires can add to...and while it is true that humans cannot hear RF...and other airborne noise....RF can interfere, in very negative ways, with the audio range that we can hear. All of the powerline devices, internal shielding in components, power supply filtering, wire shielding...etc. is based on this..it has never been that we can hear RF, it is simply that RF, in the audio amplification and wiring chain, can and does cause problems for the frequency range we can hear.