Hideo Miyazaki

Sound field reproducing method and apparatus for the same

A space surrounding a sound source (S) which is set in a sound field (10) to be reproduced is divided into sound source element regions (S1 to Sn), and a space surrounding a sound receiving point (R) is divided into sound receiving element regions (R1 to Rm). An impulse response when a sound radiated from the sound source (S) is emitted from one of the sound source element regions (S1 to Sn), passes through the sound field (10), enters one of the sound receiving element regions (R1 to Rm), and then reaches the sound receiving point (R) is obtained for each of combinations of the sound source element regions (S1 to Sn) and the sound receiving element regions (R1 to Rm). A sound emitted from a real sound source (Sr) in an arbitrary real space (26) is picked up by microphones (MC1 to MCn) placed correspondingly with the sound source element regions (S1 to Sn). In an FIR matrix circuit (42), the pickup signals are respectively subjected to a convolution operation with impulse responses which are obtained for each of the sound source element regions (S1 to Sn) in corresponding directions.

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

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 refle...

Acoustic design method of multifunctional small venues

Looking at the tendency of resent acoustic design projects in Japan, the number of venues specialized for a certain usage like concert halls is decreasing while the significant differences of the number of multi-purpose venues are not seen between in 1990s and 2000s. On the other hand, regarding the size (seating capacity), the number of over 1,000 seats multi-purpose venues are decreasing and that of below 1000 seats (especially, small venues below 500 seats) tends to be increasing. One of the reasons for this tendency is the finance problem at local governments. Another reason is the background that venues used by local citizens has been focused rather than large venues for touring performances under the strategy to activate the local cities. In this report, the acoustic design examples of multifunctional small venues are introduced while categorized by their design methods.

Hybrid measurement method in room acoustics using dodecahedron speakers and a subwoofer

A dodecahedron speaker is usually utilized for measurement in room acoustics under the hypothesis of omni directional point source. But generally speakers used for a dodecahedron speaker cannot playback low‐frequency sound such as under 100 Hz, which is important especially for auralization, while the one constructed of units with large diameter to support low‐frequency sounds cannot be considered as an omni‐directional speaker in high frequencies. To meet these requirements, a hybrid system combining a dodecahedron speaker and a subwoofer has been developed and actually used for measurements of impulse responses in acoustical design of concert halls. The summary of this method will be presented. The feasibility of this method will be also discussed while evaluating the measurement results in concert halls by changing measurement conditions such as speaker locations and comparing these results with those of conventional methods.

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...