In analysis of structures excited by noise a special function joint acceptance function should be calculated.This function represents the coupled relation between structural modes and sound modes.It is an integration of them in space.In general

this function can be obtained only in the case where the analytical experssions for both structural modes and sound modes have been established.However

for most engineering structures such as the casing of aero engine it is difficult to obtain the analytical expression for its modes (either structural or sound).The article presents the research work in view of this problem.Considering the main structural type of the aero engine

we take cylindrical shell as studied structural type.In the article it is studied how to calculate the joint acceptance function based on the result obtained by finite element method

which is used widely in structure analysis.A general numerical calculating method is presented.The result obtained by this method is compared with the analytical result.