Compact Spherical Loudspeaker Array for Variable Sound-Radiation

Diploa thesis (15.266 KB pdf)

Based on the icosahedral loudspeaker of the IEM a spherical loudspeaker array will be developed, which allows variable sound-radiation in all directions, also known as spherical beamforming. In addition to the realization of musical and artistic performances, it can also be used for room-acoustical measurements. From a mathematical point of view, a decomposition of the sound field into a series of spherical harmonics is applied, which will be played back by the loudspeaker array and thus will reproduce the desired sound field. The array consists of 16 loudspeakers, which should be uniformly arranged on the sphere. Hence a system with the resolution of third order can be realized. As the array shall be designed for high-frequency range, small extensions of the sphere and loudspeakers must be found. Therefore a compromise between compact dimensions and upper and lower cut-off frequencies must be achieved. In particular spatial aliasing should be avoided and a feasible dynamic range shall be obtained by appropiate filtering.

The work starts with the design of the spherical loudspeaker including amplification, wiring and mounting. Acoustical measurements with the completed array will be made to determine the radiation patterns of the single loudspeakers and their mutual interaction in the all-over system. A control system for the array is going to be implemented in PD. Therefore the existing angular and radial steering filters must be modified appropiately. To evaluate the results, another concluding set of measurements shall varify the system performance. The targeted application should not only work as a compact stand-alone solution, but also in combination with the existing low-mid-range icosahedral loudspeaker array.