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Active Field Control (AFC) is an innovative system that employs electroacoustic technologies enabling "natural changes" to major auditory impressions, such as liveness, loudness and spaciousness.
AFC can be used to improve the architectural acoustic characteristics of a room, and has additional applications focusing on the advantages of optimized reverberation time.
AFC controls acoustical conditions based on the existing room condition by utilizing the acoustical feedback of a system.
Therefore, AFC should be distinguished from other techniques using digital reverberators, which generate reverberation electronically.
AFC make it possible to hold classical concerts in a very large hall without SR, to accommodate an organ in a small church, and to enhance the enthusiasm of audiences in a stadium.
A reverberation time in a room can be extended by increasing the energy density. AFC actively utilizes the acoustical feedback of a system to increase the energy density of diffused sound, so that reverberation time and sound energy density can be controlled with auditory naturalness while preserving the original acoustical characteristics of a room.
Since AFC utilizes acoustical feedback, it is essential to prevent coloration problems caused by a closed loop condition and to maintain a stable system. In order to ensure smooth loop gain and a sufficient margin against howling, which prevents instability, two patented Time- varying controls, Electronic Microphone Rotator (EMR) and fluctuating FIR (fluc-FIR), are implemented in the AFC system.
Copyright (C)2008 Yamaha Corporation. All rights reserved.
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