Impedance mismatch theory and review of the blocking mass

The structure-borne sound in transmission always falls across obstructs, for example, supporting parts, tie-in and blocking mass. These obstructs could induce the impedance mismatch of the structure, reflecting and restraining the structure-borne sound, and thereby isolating the elastic waves. The impedance mismatch theory is firstly expatiated using the wave approach to make know that the more change of the impedance of the structure the more effective isolation of transmission of the elastic wave. The aim of analyzing the one-dimensional rod axial vibration model then is to examine the relationship between the isolation capacity and the change of impedance of the structure resulting from section and density change. The application and the development of the blocking mass based on impedance mismatch theory are summarized at last. Interest is also focused on the tendency of the reduction vibration technique of blocking mass.