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All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Comparing Two Statistical Models for Low Boom Dose-response Relationships with Correlated Responses

This study compares two statistical modeling approaches to construct summary dose-response curves for low boom community noise surveys. NASA field survey data were used that consist of multiple responses from a survey participant. These data require an approach that accounts for the correlation among repeated annoyance observations from the same participant. A multilevel model accounts for the correlation by allowing estimated parameters to vary with each survey participant. On the other hand, a population average model utilizes generalized estimating equations and accounts for the correlation via a user-specified within-subject correlation structure. A visual comparison of the dose-response curves for these two methods reveals similar results. When comparing specific points along the summary curves, the multilevel model yields more precise confidence bounds than the population average model. The similarity between the summary curves derived from each model lends validity to both approaches for approximating a population representative summary curve.

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NASA NTRSDate not supplied

Experiment Design Considerations for Longitudinal Community Noise Surveys

NASA is planning community noise surveys in the coming years to collect data that might enable the return of overland supersonic flight. Community noise surveys are typically cross-sectional, with only a single response per respondent. However, to determine community response to individual supersonic overflights, longitudinal surveys with repeated responses per respondent are more practical. The downside of repeated responses is the potential for response bias, such as a carryover effect in which previous test conditions affect current behavior. Subjective sonic boom listening test data collected at NASA Langley Research Center were reanalyzed to look for evidence of carryover effects. Initial results do not suggest strong carryover effects. This presentation will provide results and suggestions for experiment design of future community surveys.

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NASA NTRS2022

High Speed Inlet Distortion Test for the X 59 Low Boom Flight Demonstrator in the NASA Glenn 8-by 6-Foot Supersonic Wind Tunnel

The Low Boom Flight Demonstrator (LBFD) High Speed Inlet Distortion Test (HSIDT) was completed in the NASA Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT) using a 9.5 percent-scale propulsion model of the X–59 to evaluate the compatibility and operability of the inlet and engine integration, focusing on the inlet dynamic effects at the engine face. The model was instrumented with steady-state and high-response total pressure probes in the conventional 40-point, equal-area array at the aerodynamic interface plane (AIP). The HSIDT successfully collected high response distortion data points for the X–59 from Mach = 0 to 1.55 for a wide range of angle-of-attack, angle-of-sideslip, and inlet flow. Analyses showed that inlet dynamic distortion and inlet planar wave (or inlet buzz) were within engine limits through most of the flight envelope. The test data showed that inlet planar wave was present at Mach 1.35 and above, at airflows between idle and maximum engine airflow. Engine throttle back will need to be limited when decelerating from supersonic flight Mach to avoid these regions of inlet planar wave. The HSIDT data was also used to compare the metric SUM40, computed from the 40 high-response AIP total pressure probes, with the metric SUM4, computed from four high-response inlet static pressure probes. The data showed that SUM4 can be used as a surrogate for SUM40 during the X–59 flight test to detect inlet planar wave.

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