The Cabin Attendant call from the cabin to the flight deck (not COCKpit at NWA) is the loudest in the industry. Quite often, one will have restate a transmisson to ATC when the attendant to flt deck call is activated.
Likewise, the SELCAL chime in an A320 is pretty loud as well. How could they ignore the messages even if the radios were turned down?
ASAP's probably won't do much good because they are not single source reports of the incident. There was plenty of other coverage it seems.