Would you be able to hear the carrier wave of an amplitude modulated station, if you could hear in the MHz range, or would the high frequency be filtered out after rectification?
The AM or medium wave band extends from 526.5 kHz to 1606.5 kHz in Europe or 535 kHz to 1705 kHz in the US.
Ultrasound (not supersound! :-) frequencies range from 20kHz and up:
However, a bigger problem is that AM stations broadcast using electromagnetic radiation, whereas sound travels by acoustic waves in the air.