Title means "Quietness", "Comfortable Sound" and "Excellent Acoustics"

Nagata Acoustics News 04-10 (No.202)
Issued : October 25, 2004

"Mahoroba" Kunimi Cultural Center Opens (Nagasaki Prefecture)

by Chiaki Ishiwata

The fame of Japan's Kunimi Township extends across the entire Japanese archipelago. Each year, this southern Japanese town sends a Nagasaki Prefectural Kunimi High School soccer team to the annual all-Japan high school soccer games held during the New Year holidays.

Kunimi's loyalty to its home team pervades the entire town throughout the year. Soccer balls imprinted with the home team's signature mascot-like insignia of a cute red crab with a soccer ball between its claws can be seen displayed in expected and not-so-expected places, and local businessmen use business cards decorated with blue and yellow stripes, in keeping with the colors and pattern of the team's jersey.

Kunimi, which is one of the larger concentrations of population on Nagasaki Prefecture's Shimabara Peninsula, is also known for the natural beauty of its location on the Ariake Sea to the north of Mt. Fugen, part of the active Unzen volcanic complex. The word "mahoroba" means a place of outstanding beauty, and is a fitting way to describe the town that now has a cultural center named Mahoroba.

<< Project Overview >>

The Mahoroba Kunimi Cultural Center project began construction in July 2003 and completed in March 2004, at a cost of just under 800 million yen (US$ 7.3 million or 5.9 million Euro). Mahoroba opened to the public on April 11, 2004.

The center building is a simple, one-story facility with a hall, a library and some support rooms. The design motif of the hall's interior walls features a polka-dot pattern of panels with large circular cutouts. The polka-dot motif is repeated in other parts of the center for a unifying design theme. In particular, it is also used for the design of the library's ceiling and as the basis for the design of the center's signage. The Kyushu subsidiary of Nihon Sekkei Inc. served as the project's architectural design firm.

<< The Hall >>

Project programming for the Mahoroba Hall defined the need for a room that can accommodate a wide spectrum of activities and events. While the hall's primary purposes are for ceremonies, concerts and theatrical performances, the hall must also accommodate the needs of local town clubs and circles that will use the hall in a variety of different ways, such as a ballroom for social dancing and even for exercise classes. To meet these diverse use requirements, we designed the hall as a flat floor space of 400 sq. m. (4,306 sq. ft) and equipped it with two kinds of storable seating: (1) the moveable stands with chairs (2) individual stackable chairs.

As can be seen from the accompanying facility floor plan, we installed a wall of doors along the side of the hall adjacent to the outdoor terrace. For exhibitions and gallery-style displays, the entire terrace, foyer and hall space can be used as a single, integrated event space that draws visitors from the building's exterior into the hall.

One end of the hall has a fixed, 200 sq. m. (2,153 sq. ft) stage. While the stage does not have a fly tower, we did install the basic furnishings needed for performances, including stage curtains and lighting fixtures.

Because of budget limitations, we considered the option of not installing a stage acoustical shell. But Kunimi's residents have numerous music-focused circles and societies and none of the towns in the vicinity of Kunimi have a hall with an acoustical shell, so we ultimately decided to create a favorable stage environment for music performances by installing a simple and easy-to-deploy acoustical shell system. The acoustical panels at the rear of the stage double as the stage's cyclorama and the shell's side panels divide into four portions that rotate to double as side wings for theatrical performances. We also took into consideration the need to reflect sound from the ceiling back to the stage by adding a panel for this purpose under the catwalk built into the ceiling above the stage.


<< Opportunities to Rent Just the Hall's Stage >>

The price list for rental use of the Mahoroba Kunimi Cultural Center hall offers "stage only" rentals for the nominal charge of 300 yen per an hour. Again due to cost considerations, as well as the anticipated frequency of use, the cultural center's design did not implement a floating structural approach or other, specifically sound-isolating elements for the facility's practice and rehearsal rooms. Since the hall stage is located at the far end of the building from the library, both the project design team and others involved with the project actively encouraged the cultural center to make the stage available for rental when the hall is not in use. The concept came from a hall in a nearby community that improved its utilization rate by renting its stage to a "taiko" drum group needing a venue to practice their loud instruments.

Renting "just" the hall's stage will likely be a win-win situation for the cultural center and the community. The facility cannot realistically expect to have a 100% utilization rate for the whole hall, and while there may be some times of year when other bookings reduce the availability of "stage only" rentals, there are surely many people in the community who will eagerly take advantage of the opportunity the inexpensive "stage only" rental provides to practice or rehearse on a large hall's stage. Performers always appreciate and benefit from rehearsing in the same stage environment where they will later perform before a live audience.

<< The Hall's Active First Months of Operations >>

Since the hall's opening, I have not yet had the pleasure of attending an event in the hall. However, from the hall's website and other sources, I know that the hall's calendar filled quickly with a diverse range of events, including concerts, art exhibitions, lifelong learning classes, regional association meetings, and even a Kabuki seminar. It is wonderful to know that the hall's beginning is a strong success. As the mayor of Kunimi said at the hall's opening ceremony, our highest hope for a community cultural center is that people come to it, interact together in it, participate in activities together in it and by using it, make it a place of vitality and energy.

Sapporo Art Park's New Outdoor Stage

by Motoo Komoda

Sapporo Art Park Outdoor Stage
For nearly 10 years, Sapporo City has been building and adding to Sapporo Art Park, an outstanding combination of indoor and outdoor cultural facilities. In March 2004, the park completed the construction of its newest addition, an outdoor stage for music concerts and other performing arts events. The annual Pacific Music Festival used the new outdoor stage this past summer for its 15th festival, giving the general public its first opportunity to enjoy the visually appealing stage structure, great music and sunshine all at the same time.

Previous to commissioning the building of the outdoor stage, Sapporo City constructed an art museum and Sapporo Concert Hall "Kitara" on the grounds of Sapporo Art Park. (We featured Kitara Hall in our July 1997 issue.) The outdoor stage project may be considered the coda of the suite of new structures planned by the city for Sapporo Art Park.

The new outdoor stage replaces a hastily readied temporary stage and tent setup that was built 15 years ago to accommodate the first annual Pacific Music Festival. In the years between then and now, the wish for a better stage and for dressing rooms and other improvements continued to grow stronger year by year. Now that wish has been fulfilled, at a total project cost of 6.2 billion yen (US$57.1 million or 45.8 million Euro).

<< Teaming with An Architect Passionate about the Music >>

Sapporo City selected the outdoor stage project architect based on proposals submitted by multiple firms and gave the bid to HAU (Hokkaido Architects & Urbanists), a local, Hokkaido company. As soon as HAU's president and CEO, Mr. Kaoru Ohashi, heard of his firm's selection, he immediately took a plane to Tokyo to meet with us and ask for our participation in the project. While working with HAU and Mr. Ohashi, we learned about his passionate interest in music. His passion influenced the extraordinary dedication and efforts that he expended on the project.

Some of the key foci of the project were achieving quality acoustics, providing substantial backstage support rooms, addressing the impacts of Sapporo's snowy winters, planning for the sun's glare and changing natural light conditions, and planning road of car which carries instruments in and out. Of course, like many projects, each of these items needed to be worked within the constraints of the project's budget limitations and the pre-determined location of the project site. Throughout the design and decision-making processes, Mr. Ohashi persevered and enlisted the support of his strong, local, personal and professional network of relationships in order to achieve excellent results.

<< Overview of the Project Design >>

The roof design of the outdoor stage gives the impression of a soft, billowy cloud floating down to the park from the heavens. The strikingly modern design blends beautifully with the park's natural greenery. The stage is 24 m. (79 ft) wide by 16 m. (52 ft) deep, doubling the stage floor area of the previous, temporary stage and making concerts possible by ensembles with up to 200 players.

At its forward-most point, the roof hangs 18 m. (59 ft) above the ground. The backstage area has nine dressing rooms of assorted sizes, as well as storage space and extra lavatory facilities. These support rooms will be available for use by both the Pacific Music Festival performers and by other performers and events that may use the new outdoor stage.

<< Acoustical Specifications for the Project >>

Stage Section
Nagata Acoustics' acoustical design focused on the stage and the 500-person audience seating area under the roof's extended overhang. We provided specifications for the shape of the ceiling and stage's walls.

Concrete is the material the architect chose to build the almost entire structure. As can be seen in the accompanying photo, for the lower part of the stage rear wall and the side walls, we implemented a "zigzag" pattern of surfaces, shaped like a folding screen that has been partially stretched open. The upper portion of the rear wall of the stage is also not a straight wall. Rather, we specified a horizontally "folded" or "zigzag" pattern, with slits, for this portion of the stage rear wall.

The ceiling of the stage and the overhang were fabricated with sections of poured-on-site concrete to achieve the curved surface we required. In addition, from front to back, we specified several grades or stepped variations that made the ceiling's fabrication a difficult challenge for the builders.

<< The Ceiling's Cantilevered Design >>

A goal of the project's design was to avoid putting any supports for the roof overhang in the audience seating area. Because of the overhang's considerable weight, the design approach that was adopted places the main support beam above the stage opening, and the three sides of the stage provide the mass needed to balance the cantilever of the overhang.

<< Stage Apparatus >>

To accommodate a diverse range of performance genres, we installed battens for lighting and other stage effects from the ceiling above the stage. We also installed fixed ceiling hooks for suspending additional lighting, auxiliary loudspeakers and stage curtains.

<< Comparing the Festival's Indoor and Outdoor Performances >>

On July 17, 2004, the outdoor stage celebrated its opening ceremony with a performance by the Pacific Music Festival Orchestra. Immediately thereafter, both the Pacific Music Festival Orchestra and Sapporo Symphony Orchestra gave several performances on the outdoor stage.

On July 24 and 25, I heard the Pacific Music Festival Orchestra play the same program, first in Sapporo Concert Hall "Kitara," then at the new outdoor stage. Since the musical selections were the same for both performances, this was an excellent opportunity for me to compare the acoustics of the outdoor stage with a concert hall's acoustics. For the first half of the outdoor concert I sat in one of the seats under the roof's overhang portion, and I was very pleased with the acoustical quality. I heard the orchestra's performance well and fully enjoyed this half of the concert.

For the second half of the performance, I moved to the lawn beyond the stage roof's overhang. Here, loudspeakers are used to amplify the concert for families and other listeners relaxing on blankets or their own chairs set up on the lawn. Again, I was very pleased with the acoustical quality. The sound volume level of the loudspeakers was not too loud, and the surroundings created a pleasant visual "harmony" with the concert performance. This open-style listening environment is surely one of the benefits of an outdoor stage facility.

On the closing day of the 2004 Pacific Music Festival, the festival's chief conductor, Maestro Valery Gergiev conducted the Festival Orchestra on the outdoor stage for a "Picnic Concert." I am told that this festival finale at the new outdoor stage received resounding applause from the entire audience.

<< The Many Reasons to Visit Art Park Sapporo >>

Sapporo City and the administrators of Art Park Sapporo hope that the new outdoor stage will become the venue of choice for theater and dance groups as well as for the annual Pacific Music Festival. The park's administration is already actively promoting the outdoor stage as a rental facility. Art Park Sapporo's other attractions include an art museum and an outdoor sculpture garden, numerous painting ateliers and crafts workshops, as well as restaurants, a lodge, and a historical house (built in 1913) that was the home of Japanese novelist Takeo Arishima (1878-1923) and was moved to Art Park to preserve it and make it accessible to the public. All of these facilities and the new outdoor stage make Sapporo Art Park a content-rich destination for a day or weekend steeped in the performing and visual arts. Sapporo's autumn lasts for only a short period of time, but the multicolored fall foliage is yet an added reason to visit Art Park Sapporo at this season of the year.

Sapporo Art Park is located in Sapporo City. The address is 2-75 Art Park, Sapporo 005-0864. The telephone number is + 81-11-592-4123.

Fall 2004@Acoustical Society of Japan Conference

by Ayako Hakozaki

University of the Ryukyus
Twice a year, in the spring and the fall, the Acoustical Society of Japan (ASJ) holds a professional conference that covers a broad range of sound-related disciplines and topics. This autumn, in the midst of the typhoon season and concerns about whether typhoon No. 21 might put a dent in travel and participation plans, the conference convened at the University of the Ryukyus's Engineering School, for the three days of September 28 through September 30.

This was the first time that ASJ held a conference in Okinawa Prefecture, and the conference drew its largest participation ever, with some 670 presentations and more than 900 attendees. Participants from Nagata Acoustics presented three papers, one on MUZA Kawasaki Symphony Hall, one on Kitakami Cultural Exchange Center, and one on Matsumoto Performing Arts Centre.

<< Topics at the Building Acoustics Breakout Session >>

In this review of the conference, I will summarize some of the presentations within the discipline of building acoustics.

• Sound Isolation Strategies for Open-plan Classrooms: This presentation reported on the practical application of acoustical engineering techniques to address sound isolation problems in an open-plan classroom school layout. Open-plan classroom layouts generally have inferior sound isolation performance when compared to traditional closed classroom environments raising some complaints from teachers and administrators who work there.

The numerically analyzed strategy discussed in this presentation widened the rear area of the open space used for two classrooms and angled the walls towards the outside. In addition, the acoustician created a staggered classroom layout, thereby diminishing the sound transference from nearby classrooms by several dB.

Some sound transference and distractions may be inevitable in open-plan classrooms, but for some schools the benefits of the open-plan layouts apparently outweigh the disadvantages. The selection of an open-plan layout must be based on multiple factors among which the classrooms' acoustics considerations are an important, but not necessarily the determining consideration.

• Floor Impact Sound Transference in Residential Dwellings: Twelve presentations, including three sponsored by the Institute of Noise Control Engineering Japan (INCE-J), discussed residential sound isolation topics. These presentations focused mostly on research and findings that have immediate practical applications. New building codes instituted in Japan in the year 2000 to improve the quality of life in residential structures has resulted in a burst of interest in acoustical performance research on the part of the Japanese housing industry and residential housing developers.

In addition, also in the year 2000, the Japanese Standards Association (JIS) adopted a new method for measuring the floor impact sound on residential floors. The new method uses a rubber ball to measure the floor impact sound, instead of the tires that were used previously for this measurement. One of the presentations compared the floor impact sound measured by using rubber balls and tires and there was also a report on the lack of consistent measuring results when different people measure the floor impact sound.

• Noise Caused by Perforated Metal Exterior Systems of Hi-rise Buildings: Problems due to wind-related hissing and other noises produced by hi-rise buildings are on the rise in Japan, and one presentation shared research into this problem as it relates to the popular use of perforated metal as the skin of building exteriors. According to this presentation, a complex mechanism involving numerous factors determines whether a perforated metal exterior system will generate a noise. These factors include not only the diameter of the perforations and the percentage of perforations to solid metal, but also the pattern of the perforations and the method used to support the exterior system.

This presentation made me think about the importance of being knowledgeable about materials and the risks they pose as a first step in preventing a design from resulting in an undesirable hiss or other wind-induced noise. As a practicing acoustician, this presentation, like the earlier mentioned open-plan classroom intervention report, gave me new and valuable information and insights that I can immediately apply in my professional work.

• A Polyester Alternative to Glass Wool: One of the presentations introduced a newly developed, non-woven polyester material that exhibits about the same sound absorbency as glass wool. The new polyester material eliminates two undesirable characteristics of glass wool, namely that glass wool's fibers have a tendency to disperse into the air and that glass wool creates an itchy sensation when handled by human hands. In addition, the new polyester is white in color and inexpensive, giving it numerous benefits that will appeal to both acoustical designers and builders. For the present, however, the new product is not yet certified as non-flammable, so it unfortunately cannot be used in interiors that require non-flammable materials. This presentation also gave me information that I hope I can put to good use in my future acoustical design work.

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Nagata Acoustics News 04-10 (No.202)
Issued : October 25, 2004

Nagata Acoustics Inc.
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