Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS


News 08-03 (No.243)

Issued : March 25, 2008

[ Japanese Version ]

Mihara Performing Arts Center "Popolo," the New Hall that's Fun to Use—and to View

by Chiaki Ishiwata

The Mihara Performing Arts Center exterior
The Mihara Performing Arts Center
exterior

The hall with orchestra shell deployed
The hall with orchestra shell deployed

Looking towards the hall's audience seating from near side of the stage
Looking towards the hall's audience seating
from near side of the stage

Last autumn, in Hiroshima Prefecture's Mihara City, residents celebrated the opening of the long-awaited Mihara Performing Arts Center "Popolo." The Mihara City coastline faces Japan's Seto Inland Sea. The area is known as an abundant habitat for octopus, a seafood Japanese serve as sushi and use in other dishes. The present city boundaries reflect the 2005 merger of three towns to create the one larger municipality, which has a population greater than 106,000.

<< The Performing Arts Center's Reconstruction Project Phases and Participants >>

In 2004, with the city's then 40-year old cultural center showing signs of aging and in need of repair, the city published a request for architectural proposals to design a new center. The city received submissions from firms throughout Japan and awarded the project to Maki and Associates (Fumihiko Maki, Principal).

After the design phase of the project, construction began in 2005 and completed in September 2007. A joint venture of Kumagai Gumi Co., Ltd. and the Hiroshima-based companies Seim Co., Ltd. and Sanyo Construction Co., Ltd. built the center. Nagata Acoustics participated on the project, working directly with Maki and Associates and having responsibility for the acoustical design, related construction management and post-construction measurements.

<< The Performing Arts Center's Exterior Architectural Design >>

As I watched and participated during the project's construction phase, the building's structure underwent several striking changes. When I saw the completed steel framework that sweeps in a grand arc over the hall's audience seating section, the color and shape looked like the back of an armadillo. Thereafter, the builders added mesh forms with frames of steel trusses, poured the roof's concrete and overlaid the concrete with overlapping metal sheets to create the pillow-shaped dome of the roof shown in the accompanying photograph.

Speaking about his architectural design for the performing arts center, Mr. Maki reminded us about the baby seal that, in 2002, mistakenly found its way into Tokyo's Tama River. The adorable baby seal, given the name "Tama-chan" (roughly, "Little Ball") captured the hearts and attention of Japan. Mr. Maki said he used the dome shape in his design to create a performing arts center that will likewise have an enduring charm and forever capture the hearts and attention of the people of Mihara City.

Mihara City has a station on the Sanyo Shinkansen Line that runs between Osaka and Hakata on Kyushu Island. One side of the new cultural center's site parallels the Shinkansen tracks at a short distance from Mihara Station in the Kyushu-bound direction and train riders can now enjoy a view of the cultural center's charming "Tama-chan" dome shortly after leaving Mihara Station.

<< Location and Layout Decisions for Optimal Sound Isolation >>

The main facilities in the performing arts center include the 1,200-seat multipurpose hall, a rehearsal room, two practice rooms and a foyer that doubles as an exhibition hall. As part of our acoustical design responsibilities, we contributed to the placement of these facilities in the constrained space of the project site. As I mentioned above, one side of the site parallels the elevated railroad tracks of the Sanyo Shinkansen and Sanyo Train lines, with only a narrow street separating the site from the elevated railroad tracks. The adjacent train lines raised concerns about the possible effects of train noise and structure borne sound.

At the start of our conceptual design work, we measured the noise and vibration at the project site and, based on the results, we proposed locating the performing arts center building on the part of the site farthest from the train tracks. In addition, we specified the use of vibration mitigating materials where the foundation meets the framing of the wall that faces the train tracks and also in the foundation itself. Furthermore, in designing the interior layout of the performing arts center, we located the multipurpose hall as far from the train tracks as possible, because this is the facility with the greatest need for a quiet environment.

Our layout decision for the multipurpose hall required us to locate the rehearsal room and practice rooms on the side of the building that is closer to the train tracks. In order to provide effective sound isolation for these three rooms from the train noise and vibration, from sound and vibration generated in each of these rooms and also from sound and vibration generated in the multipurpose hall on the other side of the building, we specified anti-vibration sound isolating structural designs for the rehearsal and practice rooms. In conversation with the hall's stage technician after the hall's opening, I asked about the rooms' quietness and he confirmed that no-one notices the proximity of the rail lines during concerts in the hall.

<< The Multipurpose Hall's Room Acoustical Design >>

The design of the center's hall includes retractable orchestra shell that enables the hall to be acoustically adapted for a wide range of events from speaking engagements, ceremonies and theater performances to classical music concerts. When the orchestra shell is deployed, they create a visual and acoustical sense of continuity between the stage and the audience seating area, achieving a concert hall-like environment.

The spatial volume of the hall is 12,000 cu. m. (423,776 cu. ft). With the orchestra shell deployed, the reverberation time is 1.7 seconds (for midrange frequencies, in a fully-occupied hall). Compared with the value of the reverberation time, the perceived experience in the hall gives the impression of a longer reverberation and more expansive sound.

When the hall is set up with stage curtains, the reverberation time is 1.2 seconds (for midrange frequencies, in a fully-occupied hall), a difference of 0.5 seconds compared with the hall when the orchestra shell are deployed. This is an appropriate range of adaptability for a multipurpose hall.

<< The Loudspeakers' Concealed Location >>

Design of proscenium loudspeakers and reflection panels
Design of proscenium loudspeakers and reflection panels

In this multipurpose hall, we located loudspeakers—intended primarily for speech amplification—at the sides of the stage and above the proscenium. From the top of the stage proscenium, the hall ceiling slopes upward over the audience seating area. This part of the ceiling was divided into three triangular sections, with the middle triangle forming a point where it meets the proscenium. In the area above this point we placed the proscenium loudspeakers, camouflaging them behind a saran-covered opening. With the help of the expert workmanship of the construction crew, the saran-covered opening above the proscenium and the ceiling around the opening are practically unnoticeable from the audience seating area.

The ceiling above a hall's stage, apron and nearby areas plays a critical role in generating sound reflections and, from the perspective of the hall's room acoustics, we strongly want to avoid creating a large aperture in this part of the ceiling. From the perspective of the sound system design, each loudspeaker needs to have a satisfactorily large opening on the side where it emits sound. Developing a design that satisfies both these perspectives can be a challenge. At Mihara Performing Arts Center Hall, we installed sound reflecting panels behind the opening for the loudspeakers and on the hall side of the loudspeakers we specified a large aperture covered with acoustically transparent material. This solution was very well received by the architects.

<< The Drop Curtain's Visual Appeal >>

The hall's drop curtain
The hall's drop curtain

Including a photo of a hall's drop curtain may be unusual in Nagata Acoustics' monthly newsletter, but the Mihara Performing Arts Center Hall's drop curtain deserves mention. The curtain matches the hall like a painting in a custom frame. On this project, the client engaged the participation of the project architect in selecting the drop curtain and his input shows in the successful harmonious fit of architectural design and textile art.

<< The Performing Arts Center's Inaugural Performances >>

Following the formal inauguration ceremony, Mihara City celebrated the opening of the new performing arts center with a performance by actress and singer Chieko Baisho and an evening concert by pianist Hiroko Nakamura. During her performance, Ms. Baisho stirred the audience to great enthusiasm by coming down off the lecture platform and by her unique wit mixed with song.

For the piano concert, the program offered works of Chopin and other well-known and well-loved works. The concert showcased the spacious and comfortable feeling of the hall's acoustics. The Mihara City residents who filled the hall for the opening concert clearly enjoyed the entire evening which extended to encores and long-lasting applause.

<< Programs to Involve the Local Community On Stage >>

Last year, the performing arts center pioneered a program that lets members of the local community experience being on stage. Using the center's "Popolo" nickname, an event named "Try Popolo" was scheduled for the holiday period at year's end. Many people came to the cultural center during the weekend event and took a turn at appearing on the hall's stage.

If "Try Popolo" creates a sense of approachability and intimacy between the hall and the local community, then it will have been a true success. Outside the cultural center's foyer an expansive lawn awaits the presence of local residents, be they on their way to the hall or simply out for a stroll. I hope that everyone in Mihara will come and enjoy the new Mihara Cultural Center "Popolo," both when they have tickets in hand for a hall event and when they are simply in the neighborhood.

Nagata Acoustics to Design Stanford University's New Concert Hall Acoustics

by Dr. Yasuhisa Toyota

Stanford University
Stanford University

Stanford University, which is located just south of San Francisco in the "university town" of Palo Alto where Silicon Valley came into being, plans to build an approximately 900-seat concert hall and 500-seat theater as the main facilities of a new on-campus performing arts center. The university held a design team competition for the project during the spring and summer of 2007 and awarded the work to the team on which Nagata Acoustics participated and which has as architect the New York firm of Polshek Partnership www.polshek.com.

The selection process began with a review of submitted written proposals by the university's design team selection committee. The selection committee narrowed the participants to two architects, theater consultants and acoustical consultants and created two teams of finalists.

The two finalist teams were:

  1. William Rawn Associates (Boston) + Theatre Projects Consultants (Norwalk, CT)
    + Kirkegaard and Associates (Chicago).
  2. Polshek Partnership (N.Y.) + Fisher Dachs Associates (N.Y.) + Nagata Acoustics (L.A.)

A design meeting with the concert hall's major donor
A design meeting
with the concert hall's major donor

For the final round of the selection competition, each of the two teams conducted design workshops and were interviewed in person, after which the university awarded the project to the Polshek team. The concert hall's design and construction will be the goal of the first phase of the performing arts center project, followed by design and construction of the theater in a second phase.

The concert hall's initial plans called for a footprint of approximately 70,000 sq. ft (6,500 sq. m.) and an early estimate for concert hall-specific construction costs of US$40 million. The design portion of the project's Phase 1 will be about two years, plus an estimated two year period for construction, for a completion date in 2011. (These estimates are based on information available as of May, 2007).


Nagata Acoustics Inc.
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Hongo, Bunkyo-ku, Tokyo 113-0033 Japan
Tel: +81-3-5800-2671, Fax: +81-3-5800-2672

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Los Angeles, CA 90025, U.S.A.
Telephone: (310) 231-7818
Fax: (310) 231-7816

E-mail: info@nagata.co.jp

[ Japanese Version ]