Based on the transfer matrix method and the virtual source simulation technique,this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound-structure interaction problems under a harmonic excitation.Within any integration segment,as long as its length is small enough,along the circumferential curvilinear coordinate,the non-homogeneous matrix differential equation of an elastic ring of complex geometrical shape can berewritten in terms of the homogeneous one by the method of extended homogeneous capacityproposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulationtechnique is adopted.The source density distributed on each virtual circular curve may be ex-panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higheraccuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in thispaper.In the aspect of solution to the coupling equations,the state vectors of elastic ring inducedby the given harmonic excitation and generalized forces of coefficients of the Fourier series can beobtained respectively by using a high precision integration scheme combined with the method ofextended homogeneous capacity put forward in this paper.According to the superposition princi-ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraicequation of system can be directly constructed by using the least square approximation.Examplesof acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentratedforce are presented.Numerical results show that the method proposed is more efficient than themixed FE-BE method in common use.“,”Based on the transfer matrix method and the virtual source simulation technique, this paper proposes a novel semi-analytical and semi-numerical method for solving 2-D sound- structure interaction problems under a harmonic excitation.Within any integration segment, as long as its length is small enough,along the circumferential curvilinear coordinate,the non- homogeneous matrix differential equation of an elastic ring of complex geometrical shape can be rewritten in terms of the homogeneous one by the method of extended homogeneous capacity proposed in this paper.For the exterior fluid domain,the multi-circular virtual source simulation technique is adopted.The source density distributed on each virtual circular curve may be ex- panded as the Fourier's series.Combining with the inverse fast Fourier transformation,a higher accuracy and efficiency method for solving 2-D exterior Helmholtz's problems is presented in this paper.In the aspect of solution to the coupling equations,the state vectors of elastic ring induced by the given harmonic excitation and generalized forces of coefficients of the Fourier series can be obtained respectively by using a high precision integration scheme combined with the method of extended homogeneous capacity put forward in this paper.According to the superposition princi- ple and compatibility conditions at the interface between the elastic ring and fluid,the algebraic equation of system can be directly constructed by using the least square approximation.Examples of acoustic radiation from two typical fluid-loaded elastic rings under a harmonic concentrated force are presented.Numerical results show that the method proposed is more efficient than the mixed FE-BE method in common use.