Synthesis of rotor noise using a stationary point source array.

Coupled simulation and experimental investigations of rotor noise impose substantial resource requirements due to the complexity of rotor noise generation mechanisms. This work proposes a synthesis method utilizing a stationary point-source array to reconstruct global rotor noise as a surrogate for actual rotor noise. First, an acoustic modal expansion model for rotor aerodynamic noise is developed based on the spherical harmonic expansion of the Green's function, and an acoustic modal model for point sources in the array is established using the addition theorem. Subsequently, the coefficient relations required for sound field synthesis are derived using the orthogonality of spherical harmonics, from which the driving signals of point sources are determined. Furthermore, simulations on a 0.86 m radius rotor under various flight conditions validate the modal method against retarded-time time-domain solutions, with mean prediction error less than 0.6 dB. Finally, the synthesis method is verified by comparing the target rotor noise with the superimposed total noise derived from time-domain analytical point-source solutions, with mean synthesis error below 0.4 dB. The proposed synthesis method offers an efficient tool for rotor noise coupled simulations and propagation experiments.