Estimation of noise radiation including airborne noise using the in-situ blocked force approach (Second report, verification of the estimation method by numerical analysis of noise radiation from a cantilever rectangular plate and proposal of an estimation error reduction method)

Abstract

The in-situ blocked force approach is suitable for estimating noise radiation from a mechanical system by component tests of its active subsystem because blocked force is a specific characteristic of the active subsystem and independent from the passive subsystem or supporting structure of the component test bench for the active subsystem. However, it is reported that the in-situ blocked force approach is a methodology for estimating structure borne noise and cannot be applied to airborne noise. In this research it was found that the in-situ blocked force approach can be approximately applied to airborne noise in eigenfrequencies of the mechanical system. Therefore it was proposed to employ the in-situ blocked force approach to estimate airborne noise as an approximate method at eigenfrequencies of the mechanical system in the previous paper. In this paper the proposed estimation method was verified by numerical analysis of noise radiation from a cantilever rectangular plate. Eigenfrequencies and vibration responses of the cantilever rectangular plate were obtained by FEM and sound pressures at an observed point were calculated on the assumption that point sound sources are distributed at the all FE nodes on the whole plate surface. Furthermore, a means based on discarding small singular values in the inverse matrix method was proposed in order to reduce the estimation error which is increased in the peak frequencies of blocked forces.