Comparison of time and frequency domain analysis of propeller loading noise

This study presents a unified analytical framework for investigating the acoustic pressure generated by rotating point forces, with particular emphasis on comparing time and frequency domain formulations. While both approaches yield consistent results, each offers distinct benefits: the time domain provides intuitive insight into the contributions of steady and unsteady loading, whereas the frequency domain facilitates modal decomposition and simplifies the analysis of periodic noise. The model represents uniformly spaced blades as point forces with axial, drag, and radial components. The force magnitude varies in time according to a Gaussian pulse, enabling investigation into the influence of time scale on propeller noise. This formulation is relevant to scenarios such as rotor systems experiencing periodic loading or isolated gust encounters. Both periodic and aperiodic cases are analysed in the time and frequency domains, allowing conditions for constructive and destructive inter-blade interference to be identified. The study also examines the advantages of each formulation. Time domain analysis provides a more intuitive interpretation of aperiodic phenomena but requires careful treatment of retarded time effects. In contrast, the frequency domain is well-suited to periodic problems and naturally aligns with modal acoustic models, though it may obscure certain inter-blade interaction mechanisms. Collectively, these insights advance the understanding of rotor noise generation and its spatial characteristics in installed configurations.