Abstract: In order to improve the acoustic design of aircraft engine nacelle, a new sound radiation model of finite-length duct is put forward. A direct boundary element method is combined with transfer element method to solve this model. Using this method, the conditions of geometry and lining are less confined. Further more, this method can be developed to solve the sound radiation of a finite-length duct of continuously varying cross-sectional area.

Key words: direct boundary element method, transfer element method, aircraft engine nacelle, liner, the propagation of sound