Measuring Spatial MIMO Impulse Responses in Rooms Employing Spherical Transducer Arrays

The paper presents a new measurement method aimed to characterise completely the sound propagation form a point to another point inside a room, taking into account the directionality of the source and of the receiver. The method makes use of two spherical arrays of transducers, almost uniformly scattered on the surface of a rigid sphere, which can synthesize arbitrary polar patterns. The paper describes the beamforming method employed for synthesizing the required polar patterns over a wide frequency range, and how to process the results in various ways: graphical mapping of sound reflections inside the room, reconstructing the trajectories of such reflections and auralization, when for the first time both source and receiver can be allowed to freely rotate during the test.