6Alfredson R J,Davies P O A L.The radiation of sound from an engine exhaust.Journal Sound and Vibration,1970,13 (4):389-408.
7Sohei N,Tsuyoshi N,Takashi Y.Acoustic analysis of elliptical muffler chamber having a perforated pipe.Journal of Sound and Vibration.2006,297(3-5):761-773.