Structure-borne sound power emission from resiliently mounted fans: case studies and diagnosis

✍ Scribed by A.T. Moorhouse; B.M. Gibbs

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 664 KB
• Volume: 186
• Category: Article
• ISSN: 0022-460X
• DOI: 10.1006/jsvi.1995.0488

✦ Synopsis

A method for calculating the structure-borne sound power emission through the resilient mounts of machines is investigated by comparing calculated power with in situ measured power for a range of fans on concrete floors. The structure-borne sound power is the structure-borne equivalent of the airborne sound power of the source and is of great potential interest in predicting structure-borne sound. Initially, the simplifying assumptions invoked in the derivation are investigated by using data obtained from a typical fan installation. For the case studied it was found that the relative phases of the excitation at the various mount points could be assumed to be random, allowing significant simplification in the formulation. In addition, spatial averages of the free velocity of the machine source and the mobility of the supporting floor over the mount positions were found to be adequate. Furthermore, power transmission by rotations was shown to be insignificant compared with that due to vertical translation. These findings are not general but serve to increase confidence that acceptably accurate calculation of structure-borne sound power is feasible by using simplified formulations. Power has been calculated for four fan installations and compared with the directly measured power. In three of the cases the measured power significantly exceeded the calculated values indicating the presence of a dominant flanking transmission path (i.e., the mounts were bridged in some way). In one case the flanking via a duct support was quantified and was shown to dominate transmission through the mounts. In other cases reasonable agreement was obtained although some flanking transmission was still present.