Abstract:
Omnidirectional sources represent an integral part of acoustic measurement systems as their acceptance, particularly for dodecahedron loudspeakers, has become almost universal. For higher frequencies (above 1 kHz), the radiation pattern of an omnidirectional source loses homogeneity, since its directivity diverges significantly from an ideal spherical shape. As a consequence, the final measurement is affected by inaccuracies that can be expressed in terms of uncertainty. This paper presents a model developed to quantify the influence of the source directivity on the measurement uncertainty. The propagation of sound in rooms is simulated according to the image sources and radiosity methods. The characteristics of dodecahedron sound sources are implemented in this model with their statistical properties. and characteristic. These two core concepts are combined by means of Monte Carlo Simulations, which produce a set of synthesized impulse responses, and modelled according to the physical characteristics of a test environment and to the statistical distribution of the measured levels around the loudspeaker. The input quantities that affect the measurement uncertainty introduced by the source directivity are identified. The results are compared with measurement results, thus allowing a quality assessment of the model.