The characterization of structure-borne emission of building services machinery using the source descriptor concept

The analysis of a structure-borne sound problem is often made difficult because a universal characterization of the structure-borne emission of machines is not available. Most methods proposed characterize the machine, rather than the emission, and the problem of properly including the effect of receiver response is avoided by either choosing a particular class of machines, such as those resiliently mounted, or by classifying machines according to likely receiver configurations. Thee various mnethods proposed yield results which are physically incompatible and comparison of machines remains difficult. A source descriptor has been proposed which is calculated from source factors only, the free veiocity and component mobility. It has the dimension of power which allows comparisons of machines. Additional information on receiver mobility allows an estimnation of the structure—borne emission at the points of contact. The practicalities of measurement for a family of machines, building services, centrifugal fans, are described. Consideration is given to more than one degree of freedom of motion and for multiple supports. Simplifications in data presentation are suggested which might ensure ease of comparison of machines and a rapidly expanding and useful data base.