Well yes, signal cables very true since the impedance is relatively high - takes very little current to affect the signal. Yes even phone wiring once again since the impedance is pretty high but audio *speaker* cables are running at a very low impedance due to the fact they have a 4-8ohm speaker on the other end. For power wiring to induce any audible affect in speaker wire, would require very long distances or extremely high power runs (way past what you'd find in a house!)