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Multi-Direction Analysis in Ambisonic

Authors Deppisch, T.
Year 2019
Thesis Type Master's thesis
Topic Spatial Audio
Keywords 3D sound, acoustic source localization, Ambisonics, audio recording and reproduction, higher-order Ambisonic microphone arrays, source and receiver directivity, spherical harmonic directivities
Abstract Ambisonics is known to provide a generalised framework for recording, analysis, and playback of spatial audio signals. While recording and playback in high spatial resolution has, due to the availability of multichannel microphone and loudspeaker arrays, already been adopted by the industry, the development of signal processing algorithms for the analysis of such recordings is still a matter of ongoing research. Especially subspace-based algorithms recently proved to effectively detect the directions of multiple simultaneous sounds. Consequently, multiple direction-of-arrival detection in this thesis considers such subspace-based algorithms as a basis to introduce two new algorithms: (i) a real-valued variant of the vector-based eigenbeam ESPRIT and (ii) a variant of the spherical harmonics MUSIC algorithm that uses Newton’s method and recurrence relations of spherical harmonics to avoid an expensive grid search. Additionally, two specific applications of the algorithms are shown. The first application is an extension of the Ambisonic spatial decomposition method (ASDM) to higher Ambisonic orders and enables an enhancement of the directional resolution of Ambisonic room impulse responses by higher-order re-encoding of sound instances (acoustic reflections or diffraction) from multiple directions per times instant. The second application considers the detection of peaks and the two tangential curvatures per peak to analyse and resynthesise directivity patterns of sound sources.
Supervisors Zotter, F., Höldrich, R.