A toner wand is specifically designed to pick up and amplify very small radiated signals. All the data wiring we use is specifically designed not to pick up very small radiated signals, or to be more precise to pick them up in a way that results in them being picked up in a common mode way, which good data circuitry does not respond to. Line or mic level cabling is also designed to reject such noise. Speaker level wiring rejects such noise by its low impedance and high voltage characteristics. You're worried about signal characteristics that the wand exploits and that everything else is built to reject. Don't.