Dynamische Modenkompensation in Quaderräumen
Bachelor Thesis of Voth, Markus
In small rooms, especially with parallel and perfect reflecting walls, there occur distinct standing waves. Due to standing waves, there are constructive and destructive interferences for single, deep frequencies. In respect of the position, this inhomogeneous spread of sound pressure is perceived by the listener as an unbalanced an unpleasant soundfield. Especially in the aixCAVE the causes for standing waves exist, as mentioned above. The only possible optimization is a software solution, because walls and floor are used for rear projections. Up to now, only static software solutions are considered for the compensation of room- and transducer effects. So in this bachelor thesis it is explored, how far the spectral course of sound pressure level may be equalized in cuboid rooms with a listening position adaptive compensation of modes. Therefore an analytical frequency response estimation and an adaptive IIR-filter concept with adapted sampling rate is implemented. To reduce the computational complexity, also a symmetry optimized lookup-table concept is developed. The results of the compensation are validated with suitable simulations and measurements. In the process, the estimation of modes in the aixCAVE is proved as difficult, because of the complicated boundary conditions, appearing by an open and absorbing ceiling. With a perfect estimation, the developed software compensation of modes in the aixCAVE provides a realistic improvement of more than 20dB.