What was found
NOTICED A WEIRD HUMMING AND NOTICABLE VIBRATION DESCENDING THROUGH FL300 AND CONTINUING OFF AND ON THROUGH 3000 FT. NOTICED IT WAS STRONGEST NEAR THE MIDDLE OF CABIN BELOW MIDDLE SEATS ON LT SIDE OF AIRPLANE. WAS STRONGER AT HIGHER AIRSPEEDS INSPECTED THE LATERAL PANEL SEALS, WING ROOT FILLET PANEL SEALS & FWD WING TO FUSELAGE FAIRING SEALS. NOTED A LOOSE PIECE OF SEALANT ON LT WING ROOT FILLET PANEL & LATERAL PANEL SEAL WHERE THEY MEET. ALSO NOTED LOWER CENTER WING TO FUSELAGE FAIRING SEAL WAS NOT SECURE TO PANEL IN ANY SPOT, EXCEPT ONE LUMP TOWARDS MIDDLE OF RTV BUILT UP TO FILL THE VOID. SEAL WAS ALSO SLIGHTLY WAVY. HIGHLY SUSPECT THIS WAS CULPRIT OF HUMMING NOISE. APPLIED NEW SEALANT ON LT WING ROOT FILLET PANEL & LATERAL PANEL SEAL WHERE THEY MEET. CLEANED UP ALL OLD RTV & RESEALED & SMOOTHED OUT THE LOWER CENTER SECTION FWD WING TO FUSELAGE FAIRING SEAL FWD WING TO FUSELAGE FAIRING SEAL RTV APPLICATION WC NO E50-53-0001 1 REV 2 DATED 07 AUG 2023. NO DEFECTS NOTED.