Characteristically noise reduction in technical products like road vehicles, ships, aircraft and machines is complicated by the multitude of primary sources and transfer paths. Examples of well-known approaches for transfer path investigations are selective shielding, mechanical uncoupling, "reduced" impedance methods and simple substitution methods (e.g. loudspeakers). This paper presents a brief survey of some recently developed substitution methods which are somewhat more advanced. A characteristic feature of these methods is that the excitation of an individual transfer path is modeled on the basis of in-situ measured source or path responses. Transfer functions to receiver points are measured by invoking the reciprocity principle. For airbome sound transfer two methods are described that model a radiating surface with the aid of a distribution of point monopole sources. A "deterministic" variant uses the volume acceleration distribution and a "Statistical" variant the radiated power distribution. For structure-bome sound transfer two methods are discussed which reproduce approximately the in-situ measured vibrational response on a transfer path. One method uses linear responses (i.e. accelerations) to characterise the vibration field. The other method uses structural intensities. Some experimental results are shown as examples.
|Publication status||Published - 1992|