Selected Publications
Acoustic beamforming is widely used for source localization and line-of-bearing determination. Although many different beamforming techniques have been formulated, atmospheric turbulence effects on acoustic arrays are usually ignored in both their theoretical formulation and practical implementation. As a result, the performance of conventional beamformers, formulated for a non-turbulent atmosphere, degrades in the presence of wind velocity and temperature fluctuations, which cause fluctuations in the received signal amplitude and phase. This article presents a mathematical framework in which the amplitude and phase fluctuations are effectively suppressed from the signals allowing application of any beamforming technique and mitigating its performance degradation in a turbulent atmosphere. The framework is constrained to a single source and by the monochromatic plane wave approximation. Application of such an approach to an experiment revealed that the phase and amplitude fluctuations with spatial scales smaller than the array aperture are successfully suppressed, but the larger fluctuations (resulting in wavefront random tilt) remain and cause errors in the line of bearing estimates.
Rocket launches generate acoustic environments that impact nearby communities, motivating the need for tools to predict launch noise at the community level. RUMBLE is a computational rocket noise prediction model that produces spatial predictions of acoustic metrics but offers limited temporal resolution, complicating direct comparison with field measurements. This paper tests whether RUMBLE-predicted unweighted maximum sound levels (Lmax) agree with community-level measurements from nine Falcon 9 Block 5 launch events recorded near Cape Canaveral, Florida. Field measurements were obtained using Larson–Davis sound level meters deployed at residential distances of approximately 20–25 km from active launch pads. Because RUMBLE outputs only scalar metrics without time histories, a rolling Lmax analysis using Z-weighting and slow exponential time weighting was developed to enable direct comparison. Across nine launch events, RUMBLE-predicted Lmax values agreed with measured community levels within 5 dB, with mean absolute differences of 3.5 dB for Space Launch Complex 40 operations and 2.8 dB for Launch Complex 39A operations. These results demonstrate that Lmax is an effective scalar metric for validation of RUMBLE predictions at community locations. While the absence of time-domain and spectral outputs limits more detailed comparisons, the results provide a foundation for future model development and monitoring efforts.
On November 19, 2024, Space-X launched the sixth test flight of their Starship rocket. Measurements were made by Brigham Young University at 21 different locations around the launch pad, including two 3-meter-radius vector probes located roughly 2 km north and 2 km south of the pad. There was also an array of measurement stations near the coast ranging from 3 km south of the pad to 27 km north. Using a broadband time-correlation technique, the direction of the sound source can be determined from the vector probes. Having two vector probes potentially allows the measurement of the trajectory of the rocket as it lifts off. It was found that the small distance between the two probes limited the accuracy of the position determination when the rocket was downrange. On this launch, the super-heavy booster did not return to the launch site but was instead diverted to the Gulf of Mexico. There were two transient events that occurred after the launch which were associated with the booster-return and the hot-staging ring reentry. These sonic booms were poorly localized by the intensity probes, but well localized by the arrival times of the booms at the array of other stations.