Propagation of sound in elliptic ducts

✍ Scribed by M.V. Lowson; S. Baskaran

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 481 KB
• Volume: 38
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1016/s0022-460x(75)80003-4

✦ Synopsis

The propagation of sound in elliptic ducts has been investigated as a model case to indicate the acoustic effects of departures from symmetry in a circular duct. The cut-off frequencies of the higher order circumferential modes in an elliptic duct have been calculated for various duct eccentricities. The lowest orders demonstrate an increase in cut-off frequency with eccentricity for the odd functions and a decrease for the even, in agreement with previous work. However, the higher order modes show virtually no difference between the respective behaviours for odd and even functions and only a very small decrease in cut-off frequency compared with that of a circular duct of the same area. The practical implication of the results appears to be that even large deformations of the duct shape will have little effect providing area of cross-seetion remains constant.