Various applications of active field control (AFC)

Abstract

AFC was developed as a tool for an acoustical design and has been improved to meet various types of requirements for acoustic consulting projects. The current system is the 7th generation which consists of a hybrid of the regenerative and non-regenerative systems. The system configuration is adjusted depending on the objectives for a venue. Two unique cases of AFC applications are discussed. (1) Compensation of acoustics in the auditoria without orchestra shells. The objectives of the system are (a) the enhancement of early reflections for performers, (b) the extension of the reverberation time and the enhancement of the sound energy on the stage, and (c) the enhancement of early reflections in the audience area. 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. 2) Improvement of the acoustics under the balcony in the auditoria. The system is based on a non-regenerative system which recreates the sound field above the balcony area by using measured impulse responses. The result of the subjective experiments shows that the effectiveness of the system is significant.