This review presents an overview of advanced air mobility broadband noise (BBN) prediction and control techniques, highlighting significant advancements in various prediction models. Methods such as the semi-empirical Brooks–Pope–Marcolini (BPM) model, analytical Amiet model, and time-domain models based on the FW-H equation have been extensively studied. Machine learning (ML) shows promise in BBN prediction but requires extensive data training and application to noise source mechanisms. Passive control methods, such as leading and trailing edge serrations and blade tip designs, have been partially successful but often compromise the aerodynamic performance. Active control methods, like suction and blowing control, trim adjustments, and dielectric barrier discharge (DBD) plasma actuators, show great potential, with the latter two being particularly effective for reducing BBN in thin propeller structures. Overall, while progress has been made in understanding and predicting BBN, further research is needed to refine these methods and develop comprehensive noise control strategies. These advancements hold significant promise for effective and efficient noise mitigation in future AAM vehicles.

This study focuses on understanding the physics of noise generated by the wake interaction with the propeller. The wake is taken here as that generated by a circular cylinder. The cylinder-propeller geometry is considered here to investigate the wake effect under [ ] freestream conditions. A detached eddy simulation and Ffowcs-Williams and Hawkings equation are used to capture the tonal and broadband noise. The results indicate that the cylinder wake leads to unsteady loading, which subsequently reduces thrust and torque. The wake also intensifies the hub vortex and interacts with the tip and trailing-edge vortices, leading to enhanced vorticity and flow separation near impacted regions. Acoustic analysis shows that nonuniform inflow and blade–vortex interactions contribute to increased tonal noise, while interactions between the cylinder and propeller wakes generate significant broadband noise, especially at higher frequencies. Spectral proper orthogonal decomposition analysis confirms that both tonal and broadband noise stem from complex interactions within the turbulent wake.

This study presents a computational investigation of far-field propeller noise under edgewise inflow using Detached Eddy Simulation coupled with the Ffowcs–Williams and Hawkings formulation. The primary contribution lies in evaluating and validating surface size—with and without end cap—and end-cap correction strategies for permeable surfaces, along with a theoretical model for optimal end-cap spacing based on equations from jet-noise theory and Spectral Proper Orthogonal Decomposition. To assess these effects, smaller and larger surfaces with open ends, a single end cap, and two correction approaches—JetEnd and SPODEnd—are tested on a five-bladed propeller configuration and compared against experimental measurements. Results show that open-ended permeable surfaces substantially underpredict noise in the downstream region due to vortex leakage, whereas closed-end configurations significantly improve accuracy, with up to 97% of downstream microphones falling within 10 dB of experimental data (vs 33% for open-end). JetEnd correction provides only minor additional changes(less than 2.3 dB), indicating that spurious noise from end caps is small and largely confined to low frequencies. Both JetEnd and SPODEnd methods yield nearly identical predictions, confirming that a single end cap can predict sufficiently well. A simplified convective-spacing model is shown to align with dominant pressure-fluctuation structures extracted via Spectral Proper Orthogonal Decomposition, which means that, if correction is needed, JetEnd can be used. Limitations associated with smaller permeable surfaces highlight the need for future development of lateral boundary corrections to reduce contamination from side-edge vortex escape. While the findings are demonstrated on a specific case, the same physical reasoning suggests applicability to other propeller cases.