engleski

Concept for Active Attenuation of Aircraft Rotor Noise Using Ultrasonic Speakers

Aircraft rotors are sources of high levels of noise. Noise levels produced by helicopters and large drones are a great nuisance in urban areas. The theoretical concept of Active Noise Control (ANC) applied to aircraft rotors is presented. Concept of ANC for a ducted rotor is extended to an open rotor. Later uses ultrasonic arrays placed around the truncated cone as secondary sources of ultrasound beams of high directivity driven by the multichannel control device to diminish noise levels produced by the rotor. Amplitude modulated adjacent ultrasound beams originating from the ultrasonic arrays produce a rotational acoustic field that rotates together with the rotor. Noise cancelation by modulated ultrasound beams directed to the rotor targets the position of the dominant sources of rotor noise, i.e., rotor tips.

active noise control ; aircraft ; rotor ; sound array ; ultrasound

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