FLC OF ACR MLG ACFT MADE AN EMER DSCNT AFTER LOSING ACFT CABIN PRESSURIZATION.

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IN CRUISE AT FL310 A SUDDEN EXPLOSIVE SOUND WAS HEARD AFTER WHICH CABIN PRESSURE WAS RAPIDLY LOST. WE IMMEDIATELY DONNED OXYGEN MASKS; BEGAN EXECUTION OF EMER PROC FOR CABIN PRESSURE LOSS/RAPID DSCNT. EMER WAS DECLARED WITH ZAU (7700 SQUAWKED; ETC) AND RAPID DSCNT WAS EFFECTED TO 10000 FT. WE WERE UNABLE TO REESTABLISH CABIN PRESSURE UNTIL AT LOWER ALTS AND AIRSPDS; THEN ONLY PARTIALLY. AFTER DSNDING TO 8000 FT WE DECIDED TO FULLY DEPRESSURIZE RATHER THAN DEAL WITH PRESSURE SURGES. PAX MASKS WERE CHKED DEPLOYED; OXYGEN PRESSURE WAS GOOD; FLT ATTENDANTS CHKED IN ON OXYGEN. THE DSCNT TOOK APPROX 3 MINS. CHKLISTS WERE COMPLETED AND THE EMER WAS TERMINATED SHORTLY THEREAFTER. POINTS OF INTEREST: COFFEE BOILS VIOLENTLY WITH CABIN ALT OF 20000 FT IN COFFEE MAKERS AND COULD HAVE SPLASHED ON FLT ATTENDANTS. SUSPECT BLOWOUT WAS AT FORWARD AIRSTAIR SEALS. ATC WAS ASKING TOO MANY QUESTIONS (THOUGH THEY WERE ONLY A FEW) DURING THE DSCNT WHILE WE WERE BUSY DOING CHKLISTS. AT THE TIME THIS WAS AN IRRITANT. KEEPING EARS CLR DURING DSCNT WAS DIFFICULT. NO PAX OR FLT ATTENDANTS HAD MANY COMPLAINTS; BUT BOTH PLTS REALLY FELT IT! DECOMPRESSION WAS NOT RAPID ENOUGH TO CAUSE FOG IN THE COCKPIT.