Final Thesis

Investigations on reproduction methods using irregular near-field loudspeaker arrays

Key Info

Basic Information

Research Area:
Audio-visual Interaction,
Visualisation and Auralisation
Type of Thesis:


Bachelor Thesis of K├Ąppel, Melchior

Ambisonics is a widely used audio playback method for spatial sound reproduction by loudspeaker systems. Conventional Ambisonics decoders are based on the assumption of plane waves. For the validity of plane wave assumptions, the loudspeakers have to be placed with a constant and sufficiently large distance from the listener. However, when implementing an array in a small hearing booth, due to the limited space, the loudspeakers cannot be placed uniformly on a sphere with constant and sufficiently large radii. As a result, conventional decoders are no longer usable and the loudspeakers have to be modeled as point sources. In this thesis, a decoding method is developed and analyzed considering near-field effects and allowing loudspeakers on different radii. The spherical Fourier expansion or the wave spectra in the Spherical Harmonics domain of plane waves and point sources can be used to derive a frequency dependent near-field decoding method yielding significantly better results compared to conventional decoders. Additionally, an analysis of different array-layouts suited for the hearing booth was performed. Results indicate that irregular layouts generally perform worse than regular and angle-accurate layouts. Further investigations focus on how Tikhonov regularization can adapt and enhance the decoding method for irregular layouts. Finally, suitable layouts for the hearing booth are compared, leading to a recommendation for the practical implementation. The talk will be given in German.