Influence of source characteristics on sound attenuation in a lined circular duct

✍ Scribed by D.J. Snow

• Publisher: Elsevier Science
• Year: 1974
• Tongue: English
• Weight: 301 KB
• Volume: 37
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1016/s0022-460x(74)80026-x

✦ Synopsis

The theory used to calculate sound attenuation in a circular lined duct is briefly described.

The individual modal solutions so found are then combined in order to more truly represent the practical situation. The manner in which the modes should be combined is not normally known and some assumption such as that of equipartition of energy amongst the modes must be made. In work by Rice the modes are combined so as to form a plane pressure wave at the origin of the duct. In this paper these results are compared with those obtained by using different shapes for the original pressure wave. The two pressure wave shapes examined were selected because of their possible relevance to aero-engine source characteristics. Also different duct length to diameter ratios are investigated.

It is found that the form of pressure wave originally chosen has a marked and important effect upon the resultant attenuation and that the effect of an increasing duct length to diameter ratio is not a straightforward one.