What was found
AT CRUISE FL 340, VERT AUDIBLE SQUEAL AROUND L1 WINDOW. PERFORMED THE EXCESSIVE PRESSURE LEAKAGE CHECK OF THE FUSELAGE, TOOK THE PRESSURIZATION UP TO 4.0 PSI AND THE CABIN PRESSURE HELD FOR 2 MINUTES WITH THE #1 AND #2 PACKS OFF. CHECKED THE L1, L2, L3, R1, R2, AND R3 WINDAOWS WITH NO LEAKS NOTED AT THIS TIME, OPS/ LEAK CHECKS GOOD IAW AMM 05-51-24-2.