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William M Humphreys, Jr.

Publications and source records attributed to William M Humphreys, Jr..

5 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2023

Development of a Field-Deployable Microphone Phased Array for Airframe Noise Flyover Measurements

This technical memorandum describes in detail the construction and use of a large channel-count, field-deployable microphone phased array designed for airframe noise flyover measurements for a range of aircraft types and scales. The array incorporated 185 hardened, weather-resistant sensors suitable for outdoor use. A custom 4-mA current loop receiver circuit with temperature compensation was developed to power the sensors over extended cable lengths with minimal loss of signal-to-noise. Extensive calibrations and performance testing of the sensors were conducted to verify the design specifications. A compact data system combining sensor power, signal conditioning, and digitization was assembled for use with the array. Complementing the data system was a robust analysis system capable of near real-time presentation of beamformed and deconvolved contour plots and integrated spectra obtained from data acquired during flyover passes of the array. Additional instrumentation systems needed to process the array data were also developed, including a commercial 10-meter weather station comprised of a sonic anemometer, aspirated temperature/humidity probe and pressure sensor. Unique methods for assessing the health of the array in-situ were developed and demonstrated. A detailed mock-up of the instrumentation suite (phased array, weather station, and data processor) was performed in the NASA Langley Acoustic Development Laboratory in 2014 to vet the system performance. Issues with the sensors and electronics were identified during the mock-up and subsequently corrected. The array was then deployed for preliminary field testing at Fort A.P. Hill in Virginia in 2015 followed by the array being utilized in three separate full-scale airframe noise test campaigns at Edwards Air Force Base in California from 2016 to 2018 where the system was used to characterize the noise generated by both baseline and treated flaps and main landing gear on a commercial transport-sized vehicle.

Phased Array↗
NASA NTRSDate not supplied

Flight-Test Evaluation of Landing Gear Noise Reduction Technologies

Results from the third Acoustics Research Measurements flight test, conducted under the NASA Flight Demonstrations and Capabilities project, are presented and discussed. The test evaluated landing gear and gear cavity noise mitigation technologies installed on a NASA Gulfstream G-III. Aircraft configurations with and without main landing gear treatments were flown at several flap deflections to determine the acoustic performance of the technolo-gies for aircraft equipped with conventional Fowler flaps. With the aircraft flying an approach path and engines at “ground-idle,” extensive acoustic measurements were acquired with a phased microphone array system. Computed beamform maps were used to examine the effec-tiveness of the tested technologies in reducing the strength of the noise sources generated by the main landing gear. Various integration regions were devised to extract the farfield noise spectra associated with the treated and untreated landing gear configurations. Analyses of the gathered acoustic data demonstrate that significant noise reduction was achieved. How-ever, the full noise reduction potential of the technologies could not be determined because of contamination from flap inboard edge noise and other secondary sources.

Mehdi R Khorrami↗
NASA NTRSDate not supplied

Phased Array Characterization of Slat Noise Radiation from a High-Lift Common Research Model

A test campaign was conducted in the open-jet test section of the NASA Langley 14- by 22-Foot Subsonic Tunnel on a 10%-scale, semispan version of a High-Lift Common Research Model (CRM-HL) incorporating a leading-edge slat, trailing-edge flap and removable high-fidelity main landing gear. Far field acoustic measurements were obtained on baseline and acoustically treated model configurations using a traversing 97-microphone phased array that viewed the pressure side of the airframe. A modified version of the DAMAS deconvolution method incorporating corrections for shear layer acoustic wave decorrelation was employed to determine the locations and strengths of relevant noise sources along the span of the slat and in the vicinity of the flap edges and landing gear. The main goal of the test campaign was to use the array data to evaluate the effectiveness of various slat noise reduction concepts. It was found that slat-gap fillers produced significant broadband noise reduction for all Mach numbers and airfoil angles of attack that were investigated. Mach number scaling revealed an approximate velocity to the sixth power relationship for the slat noise at higher frequencies. Directivity measurements obtained from integration of DAMAS pressure-squared values over defined geometric zones around the model showed that baseline slat noise radiation approximated a dipole as a function of polar emission angle, becoming approximately omnidirectional with the introduction of the slat-gap filler. The test campaign clearly demonstrated the noise reduction benefits that can be obtained by applying appropriate treatments to leading edge slats on commercial transport-class aircraft.

William M Humphreys, Jr.↗
NASA NTRSDate not supplied

A Field-Deployable Wireless Data Acquisition System for Ground-Test Arrays

This paper describes the development, characterization, and deployment of a field-deployable wireless data acquisition system for ground-test arrays, applicable in noise-source localization or beamforming measurements such as those encountered during airframe noise flyover measurement tests. The system design is enabled by commercially available, low-power Internet of Things (IoT) processors and Wi-Fi communication components. Time is synchronized across the array wirelessly by leveraging the Coordinated Universal Time (UTC) time provided by the Global Positioning System (GPS). Initial laboratory characterization of the system demonstrated its ability to meet acoustic bandwidth, dynamic range, time synchronization, environmental, and battery life requirements for typical ground-test array deployments. A successful system deployment at NASA Langley was performed that included measurement of a suspended elevated static noise source, and Uncrewed Aerial System (UAS) vehicle measurements using a quadcopter operated both in hover mode and forward flight. Beamform analysis of the acquired data showed an excellent ability of the array to extract accurate sound pressure levels from the suspended source. Synchronization of the array and vehicle GPS timecodes allowed the ability to extract acoustic signatures from the UAS vehicle during hover and forward flight maneuvers over the array. These results validate that the use of a high channel count wireless array is advantageous in airframe and propulsion noise flyover test campaigns.

wireless↗