An Experimental Modal Analysis Methodology for the Vibro-Acoustical Identification of Coupled Enclosures

摘要

Structures of machinery with practical importance, such as home appliances or transportation vehicles, can be considered elastic enclosures with acoustically coupled inner spaces and any noise control procedure to be applied requires a versatile approach for their vibro-acoustical identification. A combination of methods is developed for this purpose and a domestic type refrigerator, a comparatively complex yet typical structure, is used as a case study. The method is composed of a novel experimental modal analysis technique for the determination of cavity modes that uses a set of calibrated, low cost loudspeakers as volume velocity sources, whereas, a FEM approach is used for the verification. A special emphasis is given to the effect of temperature on the acoustical modal behavior of acoustical cavities. Furthermore, the noise transmission characteristics of the structure have been investigated by using near field sound intensity measurement techniques. Finally, possible transmission paths between the sources and receiving points have also been identified in accordance with low noise design requirements. These experimental methods are integrated into a coherent procedure of measurements that can be applied to any enclosure structure of practical importance, operating at frequency ranges below 1000 Hz without any limitation on the geometry.