ORIGINS of propeller noise and possible means for its reduction both within and external to turboprop aircraft are discussed here.
Decreasing the tip speed and increasing the number of blades of turboprop propellers result in quieter performance within the aircraft but with a heavy weight penalty. Changes in certain aircraft design parameters, such as increasing clearance between fuselage wall and propeller tips, can also reduce internal noise and vibration.
Improvements in external turboprop noise can be achieved by use of quiet-type propellers, increased rate and angle of climb, preferential runways, adequate airport zoning, and sound-dissipating foliage and ground covers.