Automatic loudspeaker directivity control for sound field reconstruction

An enhancement to sound field reconstruction is proposed which improves subjective spatial perception and widens the sweet spot size of a 5 channel surround system. With the popularization of multi-channel audio systems, consumers have access to artificially generated surround sound found in movie audio tracks in addition to recordings featuring the preservation of the original audio space. How to achieve the latter is of question. A recording technique for perceptual sound field reconstruction(PSR) has been proposed by Jim Johnston et al., at AT&T. We now present an enhancement to PSR that can be applied to other surround sound systems. With most commercial surround sound reproduction, sound is directly radiated from all loudspeakers whether the original signal is direct or diffuse/reverberant. In contrast to an attack, reverberation is a far-field multipath phenomenon and reaches the ear as a sequence of decaying reflections. It is therefore desirable to reproduce recordings by scattering the diffuse field as well as radiating the direct field. In the proposed system, the direct field is radiated with a conventional loudspeaker while the diffuse sound field is separated and radiated with a loudspeaker/diffusor combination. The presented design utilizes the ear´s ability to localize sound sources while preserving the perceptual spaciousness of the sound field. A digital switch was implemented to split the fields for each direct/diffuse loudspeaker pair.