Estimation of noise radiation including airborne noise using the in-situ blocked force approach (Proposal of an approximate method and its verification using a simple model)

Abstract

This paper proposes a methodology for estimating airborne noise from a mechanical system under the operational conditions by component tests of a certain active subsystem which is a part of the mechanical system and includes all of vibration sources in the mechanical system. The mechanical system consists of the active and passive subsystems, and supporting structure of the active subsystem is different from that under the component test conditions. Hence airborne noise from the active system under these two conditions are different from each other. Therefore the in-situ blocked force approach is expected to estimate airborne noise under the operational conditions by the component tests, because blocked force is a specific characteristic of the active subsystem and independent from its supporting structure. However it is reported that the in-situ blocked force approach is suitable for estimating structure borne noise and cannot be applied to airborne noise, it has been found that the in-situ blocked force approach can be approximately applied to airborne noise in resonant frequency of the mechanical system. This paper describes theoretical derivation of the approximation error caused by applying the in-situ blocked force approach to airborne noise. Furthermore, the error is evaluated by means of a 3-DOF simple model.