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Attenuation of sound in ducts with acoustic treatment: a generalized approximate equation
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Rice, E. J. |
| Copyright Year | 1975 |
| Description | A generalized approximate equation for duct lining sound attenuation is presented. The specification of two parameters, the maximum possible attenuation and the optimum wall acoustic impedance is shown to completely determine the sound attenuation for any acoustic mode at any selected wall impedance. The equation is based on the nearly circular shape of the constant attenuation contours in the wall acoustic impedance plane. For impedances far from the optimum, the equation reduces to Morse's approximate expression. The equation can be used for initial acoustic liner design. Not least important is the illustrative nature of the solutions which provide an understanding of the duct propagation problem usually obscured in the exact calculations. Sample calculations using the approximate attenuation equation show that the peak and the bandwidth of the sound attenuation spectrum can be represented by quite simple functions of the ratio of actual wall acoustic resistance to optimum resistance. |
| File Size | 1000828 |
| Page Count | 26 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_19760005739 |
| Archival Resource Key | ark:/13960/t91882w6r |
| Language | English |
| Publisher Date | 1975-01-01 |
| Access Restriction | Open |
| Subject Keyword | Acoustics Sound Propagation Approximation Impedance Ducts Walls Linings Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
