Abstract
Ambisonics is an established framework to capture and reproduce spatial sound fields based on the spherical harmonics representation [Gerzon (1973). J. Audio Eng. Soc. 21(1), 2-10]. A generalization-spheroidal ambisonics-based on spheroidal wave functions is proposed for use with spheroidal microphone arrays. Analytical conversion from spheroidal ambisonics to spherical ambisonics are derived to ensure compatibility with the existing ambisonics ecosystem. Numerical experiments verify spheroidal ambisonics encoding and transcoding for spatial sound field recording. The sound field reconstructed from the transcoded coefficients has a zone of accurate reconstruction which is prolonged towards the long axis of a prolate spheroidal microphone array.
Highlights
Immersive multimedia technologies such as augmented reality (AR) and virtual reality (VR) are receiving much attention
The sound field reconstructed from the transcoded coefficients has a zone of accurate reconstruction which is prolonged towards the long axis of a prolate spheroidal microphone array
We describe a formulation for the case of prolate spheroidal ambisonics, allowing the use of prolate spheroidal microphone arrays in an analytical manner in contrast to a recently proposed approach which allows arbitrary shaped microphone arrays but relies on numerical simulation to encode the captured field (Zotkin et al, 2017)
Summary
Immersive multimedia technologies such as augmented reality (AR) and virtual reality (VR) are receiving much attention. Ambisonics spatial audio capturing and processing consists of a microphone array and signal processing algorithms that are used to encode the raw microphone array signals to the spherical harmonics-domain spatial description format, which is referred to as the ambisonics signal. This ambisonics signal is decoded to the signals which is fed to loudspeaker arrays to render the spatial sound field. In addition to the basic formulation, an analytical conversion formula from spheroidal ambisonics to spherical ambisonics is derived This allows the utilization of the existing ecosystem around spherical ambisonics after recording the spatial audio with a spheroidal microphone array. Numerical experiments are performed to validate and demonstrate spheroidal ambisonics encoding and transcoding when used for spatial sound field recording
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