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Multi-direction analysis in Ambisonics

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 The recent rise of virtual reality heavily promotes the use of Ambisonics as spatial audio format due to its flexibility and the computational simplicity of spatial transformations such as rotations. Another advantage is the existence of a corresponding full-sphere recording technique, gaining more and more attention as coincident microphone arrays employing a larger number of sensors are becoming commercially available. In contrast to object-based audio formats, the scene-based approach of Ambisonics does not incorporate source meta data. Hence, a recent issue in audio signal processing is to recover directional source parameters from Ambisonic recordings. For this purpose, this work utilizes the framework of eigenbeam estimation of signal parameters via rotational invariance techniques (EB-ESPRIT). Direction estimation in EB-ESPRIT is based on eigendecomposition of matrices constructed via recurrence relations of spherical harmonics. Applications include the estimation of principal source directions in Ambisonic recordings and of reflection directions in spatial room impulse responses as well as directivity pattern analysis of musical instruments. The presented algorithms are analyzed and extended by methods of statistical signal processing.
Supervisors Zotter, F., Höldrich, R.