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Ground effects on aircraft noise. [near grazing incidence
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Hilton, D. A. Willshire Jr., W. L. |
| Copyright Year | 1979 |
| Description | A flight experiment was conducted to investigate air-to-ground propagation of sound near grazing incidence. A turbojet-powered aircraft was flown at low altitudes over the ends of two microphone arrays. An eight-microphone array was positioned along a 1850 m concrete runway. The second array consisted of 12 microphones positioned parallel to the runway over grass. Twenty-eight flights were flown at altitudes ranging from 10 m to 160 m. The acoustic data recorded in the field reduced to one-third-octave band spectra and time correlated with the flight and weather information. A small portion of the data was further reduced to values of ground attenuation as a function of frequency and incidence angle by two different methods. In both methods, the acoustic signals compared originated from identical sources. Attenuation results obtained by using the two methods were in general agreement. The measured ground attenuation was largest in the frequency range of 200 to 400 Hz. A strong dependence was found between ground attenuation and incidence angle with little attenuation measured for angles of incidence greater than 10 to 15 degrees. |
| File Size | 9170195 |
| Page Count | 130 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19800004566 |
| Archival Resource Key | ark:/13960/t9g49hb03 |
| Language | English |
| Publisher Date | 1979-11-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Sound Propagation Acoustic Measurement Meteorological Parameters Noise Reduction Aircraft Noise Grazing Incidence Ground Effect Aerodynamics Turbojet Engines Tracking Position Elevation Angle 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 |
