Fukushi Kawakami

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.

Reverberation imparting device

A reverberation imparting device for electro-acoustically enhancing reverberation in acoustic space comprises a microphone disposed in the acoustic space, a loudspeaker disposed in the acoustic space for diffusing the sound picked up by the microphone, and feedback means comprising a signal processing circuit for electrically processing an electric signal corresponding to the sound picked up by the microphone, an output of the signal processing circuit being supplied to the loudspeaker. The microphone, feedback means and loudspeaker form a feedback loop. The signal processing circuit comprises a circuit for subjecting impulse responses of finite length to a convolution operation. Time axis of reflected sounds is extended and extension of reverberation time thereby is realized without depending upon loop gain. Density of reflected sounds is increased by subjecting impulse responses of finite length to a convolution operation whereby separation of reflected sounds is prevented.

Picked-up-sound recording method and apparatus

Sound picked up by a microphone of a first sound field is reproduced by a speaker of a second sound field, and a sound picked up by a microphone of the second sound field is reproduced by the speaker of the first sound field. Sound pressure detection section detects a sound pressure of a sound present in the second (or first) sound field picked up by the microphone of the second (or first) sound field, other than a sound reproduced by the speaker of the first (or second) sound field. Other sound pressure detection section detects a sound pressure with which the sound picked up by the microphone of the second (or first) sound field and reproduced by the speaker of the first (or second) sound field is picked up by the microphone of the first (or second) sound field. Sound-pressure-difference detection section adjusts a gain of an automatic gain adjustment section in such a manner that the two detected sound pressures assume a predetermined relationship. Thus, any sound picked up in one of the first and second sound fields can be reproduced in the other sound field with an enhanced sense of unity and connection between the two sound fields.

Active field control in auditoria

Abstract In this paper, technology for the control of the sound field in an auditorium by electro-acoustic means, A-SF (Assistance of Sound Field), is described. The A-SF is one of the AFC (Active Field Control) technologies which have made rapid progress due to the latest advances in digital signal processing, and is characterized by an acoustic feedback loop in the system. Methods for handling loop gain, G c (ω), to increase loudness, reverberance, spatial impression, etc., as well as technological problems, are presented on the basis of actual examples and reference to the various existing systems. In particular, the AAS (Assisted Acoustics System), developed by the Yamaha group, is used in a detailed discussion on the validity of A-SF system with an FIR filter in the feedback loop. Finally, the possibility of using an adaptive filter in A-SF is touched on.

Chair for an acoustically designed building

A chair includes a main body with a seat, openings formed in the greater part of the lower surface of the seat, a sound absorbing structure contained in the seat while facing the openings, and a louver having a series of openings defined with a number of slats that may be turned for opening and closing. The louver is located in front of the series of openings. When the seat is unoccupied, the slats of the louver are turned for opening. When the seat is occupied, the slats are turned for closing. The chair is adequate for concert halls or theaters.

A systematic study of power‐law decays in reverberation rooms

A space‐ensemble average decay curve {〈S2(t)〉}NO, obtained in a reverberation room, shows a smooth but notable curvature at low frequencies, implying a lack of diffusion. It is closely approximated by L(t), the theoretical curve for power‐law decays given by Schroeder [5th ICA, paper G31 (1965)], and can be quantitatively characterized by only two parameters for L(t), i.e., by T0 (initial decay time) and Q30 (curvature index). This allows a quantitative evaluation of the diffusion condition in the decay process, always relating it to the absorption coefficient (αrev) evaluated from the identical {〈S2(t)〉}NO. The validity of {〈S2(t)〉}NO has been verified by its application in the design of a large‐scale reverberation room (570 m3) provided with a huge rotating vane (6 m in diameter) on the ceiling. A large contribution of the vane to the linearization of {〈S2(t)〉}NO, and hence, to the increase in measured αrev has been clearly established after the construction. Theoretical analysis of the effectiveness of...

Reverberation characteristics measuring device

A device for measuring reverberation characteristics in a reverberation room by a digital squaring and integrating computation process. According to the invention, only a part of digital data of a large word length obtained by squaring and integrating a reverberation signal is selected out for computing the reverberation characteristics in accordance with a measuring environment such as integration time and duration of a test pulse. By this arrangement, circuitry for computing the reverberation characteristics can be made compact and time required for computing can be shortened without sacrificing the accuracy of measurement. Further, according to the invention, the level of an input signal can be computed and displayed by computing intermediate squared and integrated data at a certain time interval and adding this data with compensation data corresponding to a frequency band width of the input signal. The compensation data is automatically calculated in accordance with a set frequency of the test pulse so that a concise input signal level computation and display circuit can be provided.

Sound and vibration control for the Tokyo International Forum

The acousticians for the Tokyo International Forum were faced with a number of very severe noise and vibration problems related to the siting of the complex in the center of downtown Tokyo, the placement of the performance halls next to one another, and the location of a portion of the mechanical equipment on the roof. In addition, subway lines ran parallel to three of the boundaries of the structure, another line ran under the building, and the main tracks of Japan Rail ran above ground alongside the major atrium. This paper will discuss the noise criteria set for the performance rooms and other noise sensitive spaces, the noise and vibration measurements taken to determine the severity of the train‐related conditions, predictions of other noise and vibration sources, and the solutions developed by the design team to meet the criteria required by the program. Among the solutions are a secant wall surrounding the foundation, box in box construction for the four performance halls, blocking mass installatio...

Design of an auditorium where electroacoustic technology is fully available: Exhibition Hall of Yamaha Sportland TSUMAGOI

The semiopen‐type Exhibition Hall with more than 3500 seats was built in the Yamaha Sportland TSUMAGOI with the area of 1 700 000 m2. Since this hall is expected to be used for indoor sports and musical performances, it was required to make designs from the point of view quite different from the traditional auditoriums. In view of the control of sound field by the electroacoustical means, therefore, new tools have been adopted such as (1) the movable proscenium loudspeaker, (2) movable sound absorbing canvas, (3) artificial reverberation adding system, (4) multichannel public address console and delay/reverberation control console, and (5) other various types of electrical and spatial reverberation adding devices. This paper describes the idea of design for the Exhibition Hall meeting the requirements of the latest popular music involving electric musical instruments and explains the details of design and acoustic characteristics of those electronic equipments.

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...