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Model-scale sound propagation experiment
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Willshire Jr., William L. |
| Copyright Year | 1988 |
| Description | The results of a scale model propagation experiment to investigate grazing propagation above a finite impedance boundary are reported. In the experiment, a 20 x 25 ft ground plane was installed in an anechoic chamber. Propagation tests were performed over the plywood surface of the ground plane and with the ground plane covered with felt, styrofoam, and fiberboard. Tests were performed with discrete tones in the frequency range of 10 to 15 kHz. The acoustic source and microphones varied in height above the test surface from flush to 6 in. Microphones were located in a linear array up to 18 ft from the source. A preliminary experiment using the same ground plane, but only testing the plywood and felt surfaces was performed. The results of this first experiment were encouraging, but data variability and repeatability were poor, particularly, for the felt surface, making comparisons with theoretical predictions difficult. In the main experiment the sound source, microphones, microphone positioning, data acquisition, quality of the anechoic chamber, and environmental control of the anechoic chamber were improved. High-quality, repeatable acoustic data were measured in the main experiment for all four test surfaces. Comparisons with predictions are good, but limited by uncertainties of the impedance values of the test surfaces. |
| File Size | 9126897 |
| Page Count | 32 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19880013325 |
| Archival Resource Key | ark:/13960/t3sv2gk7x |
| Language | English |
| Publisher Date | 1988-04-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Anechoic Chambers Performance Tests Scale Models Data Acquisition Acoustic Propagation Performance Prediction Surface Properties Mathematical Models Ground Effect Aerodynamics Impedance Microphones Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Technical Report |
