| 主权项 |
1. A propeller system for an aircraft including an assembly for modifying a sound field of the propeller system, the propeller system comprising:
a rotor supported for rotation about a rotor axis, the rotor having a central hub and a plurality of blades each extending outwardly from the hub to a tip, the rotor and blades being operable to propel an aircraft to travel in a direction, the rotor blades defining a rotor plane perpendicular to the rotor axis, the blade tips defining a circumferential rotational path as the blades are rotated by the rotor; and an acoustic resonator having an opening disposed within a distance to the propeller blade tip that is small compared to the wavelength of the propeller's fundamental blade tone and proximate to the rotor plane, the acoustic resonator being excited by tip flow of the blade as it passes the opening, the acoustic resonator being configured and positioned so as to direct acoustic energy to modify the sound field of the propeller system at blade pass or higher harmonic frequency tones in a desired direction relative to the aircraft. |
