Uniform sound level distribution with high intelligibility optimization of loudspeakers' positions and delays in large scale open theater

摘要

In a large scale open theater, the use of electro-acoustic sound reinforcement system is needed to provide desired sound for largely distributed seating area. This can be attempted by using multiple loudspeakers. The highlight of this problem stems from the large control area whose dimension is very large, where time delays of arriving sounds from distant loudspeakers cannot be neglected. It results unsatisfactory sound quality at the seating area. It can be practically taken care by using high directivity loudspeakers independently to designated partitioned area. In this case, audience can only hear the sound from single loudspeaker, so that surround effect or spatial sound effect cannot be provided. In this paper, optimization algorithm for loudspeaker positioning and delay control is proposed. For a given number of loudspeakers, and given geometry of the theater, the optimum positions and directions of loudspeakers, and its optimum delay time for each channel is obtained by the optimization process. Three cost functions are defined to give uniform sound in the seating area at a sufficient loudness with high intelligibility. The algorithm does not consider reflections or absorptions from the ground or seats. The algorithm is used for optimization of loudspeakers in a fan-shaped open air theater. The longest distance is over 150m and 16 loudspeakers are used. The theater is assumed as two dimension shape and for each loudspeaker, optimum positions and delay times are obtained. A comparison between simulation results and listening experiment using the optimum solution of the proposed algorithm is discussed.