Noise attenuation of quadrotor using phase synchronization method

The annoying noise produced by the rotors of multi-rotor aircraft can bring severe disturbance to the residents. Hence, it is essential to reduce the noise level of multi-rotor aircraft for its further development. In this paper, an attempt is made that applying the phase synchronization method to the multi-rotor aircraft for noise reduction, and the feasibility and potential are explored by the means of simulations. Firstly, the aerodynamic noise prediction model is established by combining the free wake method and the Ffowcs Williams-Hawkings equation. On this basis, the multi-island genetic optimization algorithm is employed to obtain the optimal phase angles which can minimize the noise level at the objective positions. Then, the noise attenuation simulations of the quadrotor at a single observation and a finite region are studied with different advance ratios, and the noise attenuation mechanism is analyzed. Finally, the noise reduction benefits of the square quadrotor and the diamond quadrotor are compared. The simulation results show that, for the observation plane 5 m below the vehicle, through employing the phase synchronization method, the noise level of a single observation point can be reduced by up to 30 dB, and the noise level of the forward quarter can be reduced by up to 12 dB. Therefore, it can be confirmed that the phase synchronization method shows an excellent noise attenuation potential for quadrotor.