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Optimum-phase primal signal and radiation-filter modelling of musical instruments

Authors Zagala, F.
Year 2018
Thesis Type Master's thesis
Topic Spatial Audio
Abstract Capture of musical instruments including directivity by spherically surrounding microphone array often leads to either overly complex radiation patterns or destructive interferences at high frequencies. There, small differences in the distance from the instrument to each of the microphones yield different arrival times in the captured signal and hereby large phase differences. Therefore, be it by linear triangular or spherical harmonics interpolation, frequency-independent directional interpolation of the microphone signals can result either in spectral degradation or in a shift of the signal energy to higher orders; especially affecting high frequencies. In this work, an analysis method is proposed in order to decompose directional signals of any measured instrument into an interference-free primal signal and a directivity filter. Both the directivity filter and the primal source signal utilise only the short-term spectral magnitude of each microphone signal in order to avoid artefacts. The magnitudes are complemented by a simplified phase using phase-retrieval techniques
Supervisors Höldrich, R., Zotter, F.