Aircraft propeller noise reduction

Details Aircraft propeller noise reduction Aircraft propeller noise reduction

1986-11-12

1989-11-28

Barefoot, Galen L.

Aeronautics and astronautics

Aircraft propulsion

Screw

244 1N, 244 55, 416500, 416129, 415119, B64C 1148

Patent

active

048832405

ABSTRACT:
In one form of the invention, a counterrotating pair of aircraft propellers produces noise in the form of a frequency-modulated carrier wave. The frequency modulation allows a designer to manipulate the energy spectrum of the noise in order to, for example, place much of the acoustic energy into inaudible frequency ranges.

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NASA Publication N84-13186--Technology and Benefits of Aircraft Counter Rotation Propellers--(NASA CR-168258)-Dec. 1982, p. 10-"Introduction--Acoustics"; p. 30--Acoustic Study Results-Near Field Noise; bottom of p. 31; p. 36--. . . Far-Field Noise; pp. 53--Unequal Blade Numbers; p. 130 (Tables 1 and 2) row--Propeller-Number of Blades; p. 133--Summary, Column Number of Blades FXR.
E. J. Richards, P. J. Mead;Noise and Acoustics Fatigue in Aeronautics, 1986, pp. 198, 199.

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