Spatial Distribution of Acoustical Parameters in Concert Halls: Comparison of Different Scattered Reflections
Kenji Fujii, Takuya Hotehama, Kosuke Kato, Ryota Shimokura, Yosuke Okamoto, Yukio Suzumura and Yoichi Ando
Spatial distributions of orthogonal acoustical parameters were investigated in concert halls by the extensive acoustical measurements. The purpose of the measurements was to gain basic data about variation ranges, spatial dependencies, and interrelationships of the acoustical parameters, as well as to investigate local variation in parameters in neighboring seats. We measured two concert halls of similar size and shape, but with different scattered reflections. In one of halls, the array of circular columns is installed in front of walls. It was assumed that the local variation in parameters increases due to the scattering effect. The main results are the following.
1) Variation ranges of measured parameters are larger than their JND values, and most parameters vary systematically in the hall. Therefore, the seat positions in a hall can be divided into several groups in terms of each acoustical parameter. Listeners can choose a seat based on their preferences.
2) The local variations in SPL, the total amplitude of reflection (A-value), and the subsequent reverberation time (Tsub) in neighboring seats are quite small. A relatively small number of measurement points are sufficient to describe the spatial distributions of these parameters.
3) An array of columns installed in Tsuyama hall weaken the specular reflections from the sidewall by scattering them. As a result, the SPL and the A-value are decreased near the sidewalls. Also, the initial time delay gap (Dt1) is prolonged throughout the hall and its local variation becomes large.
Key words: acoustical parameters, spatial distribution, concert hall, subjective preference, seat selection