What was found
LOUD SQUEAL STARTED AFTER ABOUT 35 MINUTES OF FLIGHT. MEDIC CAME TO COCKPIT TO ASSIST IN LOCATING NOISE. HE WAS UNABLE TO IDENTIFY THE LOCATION. NOISE SOUNDED LIKE IT WAS ON THE RIGHT SIDE OF THE CABIN AFT OF THE COPILOT SEAT. SHORTLY AFTER, THE MASTER WARNING AND LT BLD AIR FAIL LIGHT ILLUMINATED. I EXECUTED THE UNDERLINED STEP OF THE EP AND NOTIFIED ATC REQUESTING RTB TO PASI. ATC CLEARED US DIRECT TO BKA. I INITATED THE TURN AND THEN COMPLETED THE EP. L BL AIR FAIL REMAINED ILLUMINATED. PRESSURIZATION REMAINED NORMAL NO DECENT WAS INITIATED. DURING DESCENT, AT 7500 MSL, THE RIGHT CABIN VENT WINDOW ALSO BEGAN TO LEAK. CABIN BEGAN DEPRESURIZING AT 1500 FPM. I ENLISTED THE ASSISTANCE OF ONE OF THE MEDICAL CREW TO HELP LOCATE THE NOISE. MEMORY ITEM WAS EXECUTED IMMEDIATELY, THEN THE CHECKLIST WAS DELAYED AS WE NEEDED TO INITATE A TURN PRIOR TO ENTERING CANADIAN AIRSPACE AND CONTROLLER CHANGE. CHECKLIST ITEMS WERE COMPLETED AND PRESSURIZATION WAS NORMAL. ATTEMPTED TO CONTACT ACC ON SATCOM.