What was found
WHILE AT CRUISE 41000 FELT EARS POP FOLLOWED BY A RAPID RISE IN CABIN ALTITUDE. RECEIVED A CABIN HIGH CAS MESSAGE. PERFORMED A RAPID DECENT AND ACCOMPLISHED CABIN ALT EMER DESCENT QRC CHECKLIST. WE DECLARED AN EMERGENCY AND DIVERTED TO ERI AIRPORT. PAX MASKS WERE DEPLOYED. TROUBLE SHOT AND FOUND RAM AIR CHECK VALVE DEFECTIVE REMOVED DEFECTIVE CHECK VALVE AND REPLACED AND INSTALLED WITH A SERVICABLE RAM AIR CHECK VALVE OPERATIONAL AND LEAK CHECKED GOOD COMPLETED IAW EMBRAER PHENOM 300 AMM 21-23-04-400-801.