Electronic shell―Improvement of room acoustics without orchestra shell utilizing active field control

Abstract

This paper introduces an example of Electronic Shell acoustic enhancement system that was installed in a multi-purpose hall without an orchestra shell. The system is based on the concept of Active Field Control using electro-acoustic means. The three objectives of this system were 1) the enhancement of early reflection for performers, 2) the extension of the reverberation time and the enhancement of the total sound energy on stage, and 3) the enhancement of early reflection in the audience area. The application of this system showed an improvement of about 1 to 2 dB in STearly and more than 2 dB in G in the audience area, which is equivalent or better performance than simple mobile type orchestra shell. Regarding the spatial sound structure and the time domain characteristics between simple mobile type shell and the Electronic Shell system, there are differences since the mobile type shell mainly takes care of lateral reflections; on the other hand, the Electronic Shell system takes care of overhead reflections, and it cannot provide some early reflections after the direct sound arrives. It was clarified the relationship between the differences in physical features and the subjective improvement of the musical performance using a temporal system installed in a rehearsal hall.