What was found
RAPID DECOMPRESSION AT FL310, IMMEDIATE LOSS OF CABIN PRESSURE TO A CABIN ALTITUDE AROUND 17,000 FT. DIFFERENTIAL SLOWLY DECREASED FROM THERE UNTIL THE DIFFERENTIAL WAS AT ZERO. WE WERE REQUIRED TO USE THE OXYGEN MASKS AND DESCEND TO 10,0000 FT. DURING DECENT IT WAS FOUND THAT THE CO-PILOT MIC IN THE OXYGEN MASK WAS NOT WORKING.