A proper characterisation of noise of a vibrating source has to take into account both radiation from the source and diffraction by its body in order to enable prediction of sound pressure of the source when inserted into a given acoustical space. A particular technique, named the dummy source approach, has been developed with the aim of characterising real noise sources. Here the original source is replaced by a closed rigid cabinet of similar size and shape-the dummy-equipped with several small flush-mounted drivers. The noise of the original source is measured first in a number of control points and the source strengths of the drivers are then identified by inversion. Once a source is experimentally characterised by its dummy, further noise prediction steps can be carried out in a fairly straightforward manner since the source is represented by a simple shape and its excitation is of monopole type. The paper introduces the concept of the dummy source and discusses criteria of its acoustical layout. A characterisation procedure is then carried out via a virtual experiment aimed at validating the approach. The approach is finally validated by experimental results.