Mazda Tribute Vacationer 2004 - unknown audible dash beep
 

My Tribute 2004 sounds an occasional audible alarm from somewhere in the dash. It goes every 10 mins or so for up to about 10 secs. Then it stops. There are no warning lights on, nothing is plugged into the power sockets. The only feature that doesn't work is the cruise control. All coolants and fluids are good. What might it be?