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On the propagation of plane acoustic waves in a duct with flexible and impedance walls
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Frendi, Abdelkader Vu, Bruce |
| Copyright Year | 2003 |
| Description | This Technical Memorandum (TM) discusses the harmonic and random plane acoustic waves propagating from inside a duct to its surroundings. Various duct surfaces are considered, such as rigid, flexible, and impedance. In addition, the effects of a mean flow are studied when the duct alone is considered. Results show a significant reduction in overall sound pressure levels downstream of the impedance wall for both mean flow and no mean flow cases and for a narrow duct. When a wider duct is used, the overall sound pressure level (OSPL) reduction downstream of the impedance wall is much smaller. In the far field, the directivity is such that the overall sound pressure level is reduced by about 5 decibels (dB) on the side of the impedance wall. When a flexible surface is used, the far field directivity becomes asymmetric with an increase in the OSPL on the side of the flexible surface of about 7 dB. |
| File Size | 4824816 |
| Page Count | 28 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20030032991 |
| Archival Resource Key | ark:/13960/t8z94681v |
| Language | English |
| Publisher Date | 2003-03-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Sound Waves Ducts Noise Reduction Boundary Conditions Computerized Simulation Sound Pressure Sound Propagation Acoustic Properties Launch Vehicles Asymmetry Far Fields Wall Flow Plane Waves Surface Properties Mathematical Models 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 |
