The transmission of sound through all-metallic sandwich panels with corrugated cores is investigated using the space-harmonic method. The sandwich panel is modeled as two parallel panels connected by uniformly distributed translational springs and rotational springs, with the mass of the core sheets taken as lumped mass. Based on the periodicity of the panel structure, a unit cell model is developed to provide the effective translational and rotational stiffness of the core. The model is used to investigate the influence of sound incidence angle and the inclination angle between facesheet and core sheet on the sound transmission loss (STL) of the sandwich structure. The results show that the inclination angle has a significant effect on STL, and sandwich panels with corrugated cores are more suitable for the insulation of sound having small incidence angle.