Analyzing Differences Between Predicted and Measured Sonic Boom Metrics

Recently proposed changes to the long-standing supersonic flight ban in favor of noise-based regulations in the U.S. have emphasized the importance of understanding the variability in noise that is heard at the ground due to weather variability. In preparation for X-59 flight testing, NASA performed a series of measurement campaigns known as CarpetDIEM (Carpet Determination in Entirety Measurements). The third campaign used a 30-km array of up to a dozen measurement stations in the Mojave Desert near the NASA Armstrong Flight Research Center to record sonic booms from F-15 aircraft. Measured booms and resulting metrics from 13 supersonic passes were then compared with those predicted using PCBoom 7.5, including measured weather conditions and aircraft trajectories. When looking at metrics for community noise impact, the PCBoom predictions were higher on average than measured levels. Due to unusual features present in some of the measured data, these overestimations were not consistent across all sonic booms, with some cases being significant outliers. Additionally, there were instances of measured waveforms in the shadow zone beyond the PCBoom-predicted carpet. As such, this talk will analyze the circumstances surrounding these discrepancies. [Work supported by NASA Langley Research Center through Analytical Mechanics Associates.]