An Experimental Investigation of eVTOL Flight State Variance on Noise

Experimental data collected for a custom multirotor aircraft are used to perform an analysis to relate the variability of noise levels measured on the ground to the state vector of the vehicle in hover. Data from a total of sixty-nine hover points are used to correlate the aircraft state to A-weighted Sound Pressure Levels measured at a microphone located directly underneath the aircraft. A spherical spreading normalization is applied to the data to allow data collected from different altitudes to be compared to one another. Noise levels are found to increase as vehicle attitude (orientation) and attitude rates diverge from the trim condition. The noise was found to be most sensitive to changes in yaw or yaw rate. Conversely, the noise was found to decrease as the commanded thrust of the vehicle increased. Additional analysis indicates that the mean A-weighted Sound Pressure Level increases when the variability of the vehicle flight condition is increased.