Most likely not an FCC (EMC) issue. This sounds like direct inductive coupling from speaker D class amplifier output (or power, which would be worse, but not li

Most likely not an FCC (EMC) issue. This sounds like direct inductive coupling from speaker D class amplifier output (or power, which would be worse, but not likely) circuit at <100 kHz. Below 30 MHz only conducted emissions are measured (common mode emission via cable, say, forming a large antenna together with the power grid). The emitting component may be the speaker or (unshielded) output filter (for EMC compliance!) of the amplifier. Why it is not an issue, is that magnetic field decays really rapidly, (inversely proportional to the cube of the distance [1]) and thus is not a general concern. In fact some "secure by physics" nearby communication methods like RuBee [2] relay on this. [1] https://en.wikipedia.org/wiki/Near_and_far_field https://en.wikipedia.org/wiki/Near_and_far_field [2] https://en.wikipedia.org/wiki/RuBee https://en.wikipedia.org/wiki/RuBee