Interior Noise Control of the Saab 340 Aircraft

A comprehensive development program was performed on the Saab 340 aircraft, with the goal of reducing sound levels at the passenger seats in the plane of the propellers. The test program included in-flight sound measurements and operating deflection shape measurements on the fuselage structure, for various propeller speeds and synchrophase angles, and structural frequency response tests. The noise control approach developed was to reduce the low-order fuselage response with the addition of viscoelastic tuned dampers to the fuselage frames in the plane of the propellers.