Acoustical evaluation and control of normal room modes

Abstract

Analysis of a new criterion for the correct distribution of normal room modes is presented. This criterion replaces unsuccessful earlier ones. It is based on the resonance modes density curve related to one-third octaves. A computer program, easy to perform, allows to obtain the best dimensional ratio of the room, to avoid sound coloration. This method was duly verified, applying it to the calculation of the dimensions of a high number of existing studios considered of excellent quality and of others with evidence of coloring. The correspondence of theoretical and practical conclusions was very good. As second step, it will describe a special device for acoustical absorption. This resonant absorber is frequency selective with high absorption in the low-frequency end, remaining low and constant beyond 2000 Hz. By means of a computer program, the spatial distribution of the isolated room modes can be plotted. It allows to place the absorption devices in the exact position to obtain maximum control of each mode.