Room acoustical parameters: A factor analysis approach

In this study, we determined the most representative acoustical parameters for halls intended for verbal or music audition. Our study was carried out in nine halls of different shapes and designed for different uses. We measured the impulse response at a great number of points (many more than the minimum required by the ISO 3382 norm). From a physical viewpoint, all halls are enclosed three-dimensional areas. Our work hypothesis is that objective (measurable) acoustical parameters, or a combination of such parameters, must provide the acoustical information specific to each hall and must make it possible to grade each hall. Factor analysis was used to obtain these grading parameters and the considerable number of measurements we determined guaranteed the application of this type of analysis. The convergence provides corroboration of the main correlations between parameters. A group of orthogonal parameters was thus obtained, made up of three factors that group the parameters used by different outstanding researchers. These factors provide a clear acoustical interpretation. We have termed the first of these “intelligibility” as it contains intelligibility parameters; the second is associated with spaciousness; the third and last parameter has been termed “strength” as it is a linear combination of the parameters that measure the amplification (G) and the bass ratio (BR). The optimal scores of these factors for different uses of halls make it possible to grade any hall, independently of its shape, for its corresponding use.