Filter design for real-time ambisonics encoding during wave-based acoustic simulations

Iain Henderson, Archontis Politis, Stefan Bilbao

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

The ambisonics format is a powerful audio tool de-signed for spatial encoding of the pressure field. Anunder-exploited feature of this format is that it can bedirectly extracted from virtual acoustics simulations.Finite Difference Time Domain (FDTD) simulations areparticularly adapted as they simplify greatly the prob-lem of extracting spatially-encoded signals, and enablereal-time processing of the simulated pressure field. Inthis short contribution, we first write a time domainrepresentation of the ambisonics channels, in terms ofspatial derivatives of the acoustic field at the receiver lo-cation, and formulated as a set of ordinary differentialequations. We show that in general, the natural cor-responding discrete recursive integration yields a pro-hibitive polynomial drift in time. We then describe areal-time filtering strategy which stabilizes this numer-ical integration; in the discrete-time setting of FDTDsimulations, this real-time filtering process featuresvery low computational costs, avoiding the latency as-sociated with large convolutions and frequency-domainblock processing of previous approaches.
Original languageEnglish
Title of host publicationProceedings of Forum Acusticum
Place of PublicationLyon, France
Number of pages7
Publication statusAccepted/In press - 31 Oct 2020

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