Abstract: In discussion backscattering from a finite object due to a narrow sound beam,a hybrid (wave/geometrical) theory is proposed.In this paper,a finite-length rigid circular cylinder is considered.The incident wave beam is expanded by means of Fourier transformation in space domain and is expressed as a plane wave with a beam factor.Using the geometrical theory of diffraction (GTD) the backscattering from a finite-length rigid circular cylinder due to a narrow sound beam is obtained.It is shown that the solution predicted by the hybrid theory is fairly confirmed by the model experiment.