What was found
CREW REPORTS LOUD CABIN SQUEALING NOISE DURING CLIMB BETWEEN 6000 FT AND 7000 FT DURING ENGINE AND WING ANTI ICE SELF-TEST. THE NOISE LASTED 5-10 SECONDS AND DISSIPATED ENTIRELY AFTER SELF-TEST CONCLUSION. DURING DESCENT, CREW TESTED ANTI-ICE AT DIFFERENT ALTITUDES AND CONFIGURATIONS AND CONCLUDED THAT NOISE WOULD ONLY PRESENT ITSELF WHEN ANTI-ICE ALL WAS ACTIVE BELOW 12,000 FT. NOISE BECAME MORE PROMINENT AT LOWER ALTITUDES AND WAS HEARD ONLY ON THE LEFT SIDE OF THE AIRCRAFT. REPLACED LH WING CENTER LEADING-EDGE PICCOLO TUBE. REPLACED LT WING INBOARD LEADING-EDGE ASSEMBLY. NO DEFECTS NOTED DURING AND LEAK CHECKS OF WING ANTI-ICE SYSTEM. WORK COMPLETED IAW 57-40-00 + 30-12-00.