Comparison of Two Propeller Source Models for Aircraft Interior Noise Studies

Summary

The advanced turboprop (ATP) engines currently under development for transport aircraft are expected to be significantly noisier than existing turboprop engines. If this proves to be the case, public acceptance and thus the ultimate success of the ATP will depend on the degree to which the passenger cabin can be isolated from propeller noise. This raises the possibility that much of the gain in fuel efficiency anticipated for the ATP-powered transport could be lost because of the weight penalty associated with passive interior noise control techniques. This concern has led to a concerted effort to develop noise control methods that do not significantly increase take-off weight. One such technique being considered is synchrophasing, in which the phase angle between propellers on opposite sides of the fuselage is controlled to a value which minimizes the sound pressure level at typical cabin interior locations. The present article investigates the sensitivity of the predicted synchrophasing effectiveness trends to the propeller source model used. The influence on synchrophasing effectiveness of the relative direction of rotation of the two propellers is also investigated.