Sec.  73.403   Digital audio broadcasting service requirements.

   (a)  Broadcast  radio  stations  using IBOC must transmit at least one
   over-the-air  digital  audio programming stream at no direct charge to
   listeners. In addition, a broadcast radio station must simulcast its analog
   audio programming on one of its digital audio programming streams. The DAB
   audio programming stream that is provided pursuant to this paragraph must be
   at least comparable in sound quality to the analog programming service
   currently provided to listeners.

   (b) Emergency information. The emergency information requirements found in
    Sec. 73.1250 shall apply to all free DAB programming streams.