Spatial analysis of sound fields in rooms using spherical MIMO systems

Abstract

The perception of sound by human listeners in a room has been shown to be affected by the spatial attributes of the sound field. These spatial attributes have been studied using microphone and loudspeaker arrays separately. Systems that combine both loudspeaker and microphone arrays, termed multiple-input multiple-output (MIMO) systems, facilitate enhanced spatial analysis compared to systems with a single array, thanks to the simultaneous use of the arrays and the additional spatial diversity. Using MIMO systems, room impulse responses (RIRs) can be presented using matrix notation, which enables a unique study of a sound field’s spatial attributes, employing methods from linear algebra. For example, a matrix’s rank and null space can be studied to reveal spatial information on a room, such as the number of dominant room reflections and their direction of arrival to the microphone array and the direction of radiation from the loudspeaker array. In this contribution, a theory of the spatial analysis of a sound field using a MIMO system comprised of spherical arrays is developed and a simulation study is presented. In the study, tools proposed for processing MIMO RIRs with the aim of revealing valuable information about acoustic reflections paths are evaluated.