Thesis

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A Rigid Double Cone Microphone Array Prototype

Authors Pausch, F.
Year 2013
Thesis Type Diploma thesis
Topic Spatial Audio
Keywords Ambisonics, Akustik, Aufnahme- und Wiedergabetechnik, Surround, Signalverarbeitung
Abstract Alternatively to AB, XY or equivalence-stereophony-based surround recordings, spherical arrays have been investigated thoroughly in recent years as they permit recordings with high-resolution imaging of spatial sound. Nevertheless, this type of surround sound imaging is still a challenging research area. The particular challenge is that we have to trade hardware effort off against signal-to-interference ratio or resolution of the three-dimensional sound field capture. The prototype presented in this thesis tries to escape this narrow trade-off by a variation of the spherical geometry. All involved microphones are distributed on a spherical segment that is confined by two rigid cones to exclude a defined, unneeded range of spatial directions. Compared to a full spherical array, this permits an increased density of microphones for the desired panoramic recording angle without increased electronic hardware effort. The rigid cones are considered when solving the wave equation in terms of suitable angular solutions which are represented by modified spherical basis functions, the so-called spherical segment harmonics (SSH). Practical decomposition into SSH using a microphone array requires an array layout that provides a minimal condition number for the decomposition. An optimal layout is obtained by an algorithm that selects optimal positions from a dense grid of predefined nodes. The double cone microphone array prototype is evaluated by employing its acoustic measurement data in the analytic beamformer model.
URL http://phaidra.kug.ac.at/o:11147
Supervisors Zotter, F., Pomberger, H.