Application of Accelerated H-Matrix Boundary Element Methods to Predict Exterior eVTOL Acoustics

The development of Advanced Air Mobility vehicles such as eVTOLs presents unique challenges - both community noise and vehicle interior noise must meet targets for level and character of sound for a vehicle to be commercially viable. Community noise entirely depends on, and interior noise strongly depends on the exterior noise sources generated by the vehicle propulsion. To predict community and interior noise with models which can be used to explore improvements to meet noise targets, the exterior noise field from the vehicle propulsion must be captured with sufficient accuracy. Boundary Element Methods (BEM) have good capabilities for predicting vehicle exterior acoustic propagation, but standard BEM is challenged to predict necessary high frequencies due to small mesh size and computational limitations. Accelerated or reduced methods such as H-Matrix BEM approach can be used to increase the prediction upper frequency limit, improve calculation time, or reduce memory consumption with minimal loss of accuracy. This allows community noise to be predicted and for generation of exterior field loads on the vehicle structure to predict interior noise and design treatments. The processes and improvements offered by H-Matrix BEM in conjunction with and as an alternative to other acoustic simulation methods are discussed and presented.