Analysis of a Spatially Discrete Sound Field Synthesis Array in a Reflective Environment

Regular paper

Vera Erbes

University of Rostock

Wednesday 3 june, 2015, 09:20 - 09:40

0.9 Athens (118)

While the foundations of sound field synthesis demand an anechoic environment, this requirement cannot be met in real-world installations. Reflections at the walls of the listening room modify the synthesised sound field. Moreover, the synthesised sound field in a reflective environment, of e.g. a virtual point source, differs from the one of a real point source in the same environment. Filtered copies of the direct sound from each loudspeaker are mingled with spatial aliasing artefacts due to room reflections and a finite distance between loudspeakers, respectively. In a setup with typical loudspeaker spacings, the additional wave fronts that constitute spatial aliasing artefacts occur in a shorter timeframe than the early reflections of the listening room. This paper investigates how early reflections are filled in by these additional wave fronts produced by spatially discrete secondary source distributions. Different scenarios with real and virtual point sources in the free field and in a reflective environment are simulated. The reflective environment is simulated by an image source model. The spacing of the secondary sources is varied to generate different sequences of additional wave fronts. The resulting (room) impulse responses are analysed with respect to the structure and density of reflections and/or aliasing. Room acoustic measures like the reverberation time and early decay time of the system are considered. Finally, findings in the literature concerned with the perception of early reflections and diffuse reverberation allow for concluding on the perceptive impact of the listening room.

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