As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CRUISE ALTITUDE OF 40,000 FEET THE PILOTS HEARD A POP FOLLOWED BY A LOSS OF PRESSURIZATION. AN EMERGENCY WAS DECLARED, AN EMERGENCY DECENT MADE TO 15,000 FEET. THE AIRCRAFT RETURNED TO KRIC AND MADE A NORMAL LANDING. INVESTIGATION IDENTIFIED A RUPTURED BLEED AIR MUFFLER P/N 12945-096-801. THE UNIT WAS REMOVED AND SENT OUT FOR REPAIR. IT WAS INSTALLED AND THE PRESSURIZATION SYSTEM OPERATED NORMALLY.