Analysis of concert hall acoustics using time-frequency and time-spatial responses

A set of objective parameters (ISO3382-1:2009) is widely used for describing acoustic conditions in performance spaces. With few exceptions, they are based on integrating sound energy within moderate time intervals. In practice, different acoustic conditions can yield similar values for objective measures. A presented method of analyzing concert hall acoustics with respect to the time-frequency features aims to overcome the deficiencies of the objective parameters by conveying considerably more information in an uncomplicated form. This is achieved by visualizing the contribution of short time frames in the impulse response to the cumulative sound energy as a function of frequency. Particularly the early part of the room impulse response, including the influence of the seat dip effect is efficiently visualized. The method is applied to acoustic measurements conducted at five corresponding positions in six concert halls. It is shown that in addition to communicating standard monaural objective parameters, the visualizations from the method are connected with several features regarding the subjective impression of the acoustics. The time-frequency analysis is further extended into utilizing a recent sound direction estimation technique. Resulting time-directional visualization enables the accurate analysis of early reflections and their contribution to spatial sound.