Abstract: Based on wave propagation,formulations of transmission loss for flexural wave of an infinite rod with a blocked mass are derived.Characteristics of transmission loss for flexural wave of an infinite rod with a blocked mass are analyzed.Theoretical results show that transmission loss for flexural wave does not exceed 3dB when the blocked mass is only considered as a pure point mass.When the blocked mass is regarded as pure moment of inertia,there exists a particular frequency at which the blocked mass can completely impede the flexural wave propagation.At very high frequencies,transmission loss is approximately 3dB.When the blocked mass is considered as both mass and moment of inertia,transmission loss may be greatly improved.In applications,tran-smission loss is relevant to three parameters: magnitude,radius of gyration of the mass,and radius of gyration of the rod.In principle,increasing magnitude and radius of gyration of the mass can improve transmission loss within engineering limits.If the rod is selected,decreasing the radius of gyration is also an effective way to improve transmission loss.