Auralisation of partial sound sources

Sammanfattning: This Licentiate thesis focuses on the development of a method for auralisation of partial sound sources. In many work environments, noise is a primary annoyance factor. A specific problem is the masking of important aural information either by high noise levels or by too efficient sound insulation. A typical sound environment is made up of sound from a large number of sources. In order to improve the sound quality in such environments the noise control engineer needs a tool to find a proper balance between contributing sources. The aim of the proposed method is to properly reproduce the contribution from sources of importance. The method includes: Recording of sound pressure time signals in dedicated positions, Reciprocal measurement of frequency response functions, Sound power measurement of partial sound sources, Calculation of Cross-spectral matrix Sqq, Calculation of filters, Filter sound pressure recording to obtain time signals of the individual sources. Paper A shows an initial approach to the problem. In this work the significance of matrix inversion was not fully understood, necessary procedural measures were not used, and therefore the result was not satisfying. Paper B begins to develop general considerations regarding the inverse problem. Aspects of filtering, input interference and the uniqueness of frequency response functions are, however, not properly solved. In Paper C the result yielded good agreement between calculated and measured time signals, especially in the important frequency range 100-3000 Hz. In this frequency range, the standard deviation of the found differences is 3 dB. The audible effects of the errors in the calculated time histories are detectable but not pronounced. Finally, goals for further research are proposed.