3D Sound Characterisation in Theatres Employing Microphone Arrays

Abstract

SummaryThe analysis of the sound field's3Dproperties has been strongly improvedinrecent years, after spatial properties of sound propagation have been acknowledged to be important during the design or correction of theatres and auditoria. Besides, ap roper assessment of spatial accuracyi sr equested for 3D sound reproduction systems, initially designed for acoustical virtual reality and nowalso employed in the entertainment/cinema industry (Immsound, Auro-3D, NHK 22.2). Often only monoaural or binaural measurements are performed by means of omni-directional microphones and dummy heads, although international standards likeISO 3382/1:2009 also define some "truly spatial" parameters such as JLFand JLFC. The twolatter parameters are derivedfrom measurements made with apressure velocity (p/v)microphone, butthis is still a2-channel measurement. 3D Impulse Responses (4-channel B-format)h avef or manyy ears been measured and employed for sound reproduction. Recently,higher-order 3D Impulse Responses have been measurable thanks to the availability of compact microphone arrays employing amuch larger number of transducers. In this paper,two procedures for measuring and analysing the complete spatial sound information are presented, which are aimed at creating easy-to-understand images and videos showing the direction-of-arrivalofthe room reflections. The description of these techniques is emphasised. Furthermore, results are illustrated of experiments conducted with the novelm ethodologies in different rooms, including some ancient theatres.

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