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NASA Langley Research Center - Aeroacoustics Branch
Intern and Mentee | June 2022 – April 2023
At NASA Langley Research Center’s Aeroacoustics Branch, I investigated how different ground surfaces influence the propagation and measurement of aircraft noise. The goal was to better understand the accuracy of common outdoor acoustic testing configurations and determine whether elevated microphones could provide results comparable to microphones placed over acoustically hard ground boards. This research was done with the goal to improve aircraft noise modeling and the development of future FAA testing standards for conventional and Urban Air Mobility aircraft.
Purpose
Purpose
Investigated how ground surfaces influence aircraft noise propagation and acoustic measurement accuracy. The research compared acoustically hard ground boards with elevated microphone configurations to better understand ground impedance effects and support future FAA noise-testing standards for conventional and Urban Air Mobility aircraft.
Experiment Design
Experiment Design
Designed and conducted a large-scale outdoor acoustic experiment using multiple microphone arrays positioned over asphalt and grass surfaces. A portable speaker generated discrete frequencies, broadband noise, and multisine signals at several incident angles. I used MATLAB to process raw microphone voltage data, perform Fourier transform analysis, and compare sound attenuation across frequencies, surfaces, and microphone configurations.
Data and Results:
Data and Results:
The results showed that attenuation depended strongly on both frequency and incident angle. Lower frequencies experienced measurable ground attenuation at higher incident angles, while frequencies above approximately 1 kHz showed minimal attenuation. The study provided experimental data for improving aircraft noise prediction models and evaluating future acoustic testing methods.
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