Implementing a spherical microphone array to determine 3D sound propagation in the 'Teatro 1763' in Bologna, Italy

A new method for recording the spatial properties of a soundfield, or for generating a synthetic three-dimensional soundfield, is described. The spatial distribution of sound waves passing at a point in space is sampled by means of a number of virtual directive microphones, covering the surface of a sphere. This corresponds to a discretization of the spatial information, which is exactly the spatial equivalent of the PCM sampling of a waveform. The paper shows how it is possible to obtain information about the direction of early reflections in a theatre, not only by means of a 32-channels microphone, but also by means of traditional Bformat microphone (Soundfield). The method is applied to a historical Italian theatre, located in Bologna, i.e. the 1763 theatre in Villa Mazzacorati. The post processing includes the visualisation of the early reflections on a panoramic picture of the theatre, in which early reflections are reported as different circles on the figure, where the dimension and the intensity are related with the characteristics of the reflections. Moreover, the influence of the height of the microphone in the calculation of the acoustic parameters was analysed. The measurements were repeated at different height and different position on a transversal line in the theatre, and statistically analysed.