Shinji Kishinaga

Method and apparatus for controlling the sound field in auditoriums

A system for controlling the second field in auditorium having the feature that stage and audience seating areas are different acoustically, which includes a first assisted acoustics system whereby acoustical energy from the stage area is input, and then controlled acoustic energy is supplied to the audience seating area, and a second assisted acoustics which is provided independently of the first electronic acoustical augmentation system, whereby acoustical energy from the audience seating area is input, and then controlled acoustic energy is supplied to the stage area. Each assisted acoustics system includes acoustic energy input devices and acoustic energy output devices whereby a uniform rate of power decay coefficient can be effected throughout the hall, including spaces under balconies and the like. Significantly improved the degree of acoustic similarity between the stage area and audience seating area is achieved by controlling reverberation characteristics.

New underwater sound system for synchronized swimming: The 9th International Swimming Federation Championships

There have been concerns about the differences between underwater sound fields in a temporary fiberglass‐reinforced plastic (FRP) pool and in a conventional reinforced concrete (RC) pool. A temporary FRP pool was to be used for competitions at the World Swimming Championships in Fukuoka. We considered three items as key factors for a swimming pool used for synchronized swimming: (1) the sound source itself (output level, fluctuations in frequency characteristics); (2) the effect of materials used in pool construction upon sound source installation conditions; and (3) the effect of the mth mode low‐frequency cutoff in ‘‘shallow water.’’ To improve basic problems related to the first factor, we developed a new actuator‐driven underwater sound system (YALAS), which can eliminate the effect of installation conditions for underwater speakers in the FRP pool. This new underwater system has now seen practical use in competitions. The report summarizes this new underwater sound system and compares the system with...

Various applications of active field control (AFC)

AFC is an electro‐acoustic enhancement system, which has been under development at Yamaha Corporation. In this paper, several types of various AFC applications are discussed, while referring to representative projects for each application in Japan. (1) Realization of acoustics in a huge hall to classical music program, e.g., Tokyo International Forum. This venue is a multipurpose hall with approximately 5000 seats. AFC achieves loudness and reverberance equivalent to those of a hall with 2500 seats or fewer. (2) Optimization of acoustics for a variety of programs, e.g., Arkas Sasebo. AFC is used to create the optimum acoustics for each program, such as reverberance for classical concerts, acoustical support for opera singers, uniformity throughout the hall from the stage to under‐balcony area, etc. (3) Control of room shape acoustical effect, e.g., Osaka Central Public Hall: In this renovation project, preservation of historically important architecture in the original form is required. AFC is installed t...

Active field control (AFC) ‐electro‐acoustic enhancement system using acoustical feedback control

AFC is an electro‐acoustic enhancement system using FIR filters to optimize auditory impressions, such as liveness, loudness, and spaciousness. This system has been under development at Yamaha Corporation for more than 15 years and has been installed in approximately 50 venues in Japan to date. AFC utilizes feedback control techniques for recreation of reverberation from the physical reverberation of the room. In order to prevent coloration problems caused by a closed loop condition, two types of time‐varying control techniques are implemented in the AFC system to ensure smooth loop gain and a sufficient margin in frequency characteristics to prevent instability. Those are: (a) EMR (electric microphone rotator) ‐smoothing frequency responses between microphones and speakers by changing the combinations of inputs and outputs periodically; (b) fluctuating‐FIR ‐smoothing frequency responses of FIR filters and preventing coloration problems caused by fixed FIR filters, by moving each FIR tap periodically on t...

An algorithm for generating reverberation as an application of the chaos technique—Return map derived from initial responses

To synthesize the acoustics of a large enclosure with the aid of a computer, an algorithm for adding reverberation to the initial response is proposed. When the initial response is known, the arrival time and the intensity for each subsequent reflective sound are calculated one after another. After calculating the time intervals between each succeeding initial reflective sound and processing them to form a suitable random‐number generator, each future arrival time is then successively determined. From this generator, a return map, often used in the chaos technique, is adopted. As for the intensity, with the input value of reverberation time (RT60) the decay rate is determined; from this, the decay rate and the cumulative intensity of the initial reflective‐sound decay curve as a standard are estimated. Then each future intensity is determined by comparing the cumulative values to the standard. No awkwardness was heard from the burst tone convoluted with such a calculated response. Dimensional analysis abo...

Physical parameters for on‐stage acoustics based on optimal design for a rehearsal room

Architectural and acoustical conditions of an auditorium stage in comparison with a rehearsal room were studied in order to obtain a physical parameter for on‐stage acoustics. The basic assumptions are as follows: (1) The auditorium is acoustically divided into two spaces: the stage and the seats. (2) The final aim of designing the rehearsal room is to realize the acoustic properties of the stage. (3) The properties of the sound field for the room are determined by the room’s materials, shape, and volume. It is an important fact that their fandamental properties are influenced by the basic architectural conditions. As a result four parameters have been proposed: α (EDT), ST, RT, and the ts‐ratio (between stage and seats). They are shown as representative measures relating to sound absorption and shape in the stage area, volume of the seats, and acoustical similarity between the stage and the seats. In order to check the validity of these parameters, they were applied to the acoustical design of the rehear...