What was found
PASSING APROX. 15,000 FT WE HAD A LEVEL 2 ALERT "CABIN INFLO LO" THIS ALERT ONLY REMAINED FOR A FEW SECONDS, BUT WAS FOLLOWED BY LEVEL 1 ALERT "CABIN RATE". THERE WAS NEXT A LOUD SQUEALING NOISE FOLLOWED BY A LOUD BOOM AND SUBSEQUENT LOSS OF CABIN PRESSURE CONTROL. NEXT WE HAD A LEVEL 3 ALERT "CABIN ALTITUDE". FOLLOWED QRH, DECLARED EMERGENCY AND RETURNED TO KMEM. THE AIRCRAFT NEVER CLIMBED ABOVE FL240 AND THE CABIN ALTITUDE MAXED AT ABOUT 12,000 FT. FOUND FWD AVIONICS DOOR SEAL TORN. REMOVED AND REPLACED FWD AVIONICS DOOR SEAL, PRESSURIZED AIRCRAFT UP TO 4.0 PSI, IAW MD-10 MM 21-31-00-5-1 AND 21-00-00-5. FOUND NO LEAKS AROUND DOOR SEAL. NO OTHER FAULTS NOTED. A/C OK FOR SERVICE.