What was found
FLT#851, BOS-JFK. (AIRCRAFT PERFORMED AN AIR TURN BACK TO BOS) ' CA WINDOW HAD VERY LOUD HISSING/AIR CLIMBING THROUGH 2500MSL FOLLOWS BY 3' POPPING NOISE FROM THE CA WINDOW AREA; INSPECTED CAPTAIN WINDSHEILD AND DIRECT VISION WINDOW IAW AMM 56-12-00. NO HISSING/POPS OR LEAKS NOTED AROUND FLIGHT DECK WINDOWS, AC DOORS, OR AVIONICS COMP[ARTMENTS, A/C OKAY FOR SVC.'