News 15-02 (No.326)
Issued : February 25, 2015
In Hiroshima Prefecture, Miyoshi Civic Hall “Kiriri” Opens
By Ryoichi Wada
Miyoshi Civic Hall Exterior
Hiroshima Prefecture’s Miyoshi City is known in Japan as “Fog City”. Ironically, when the Nagata Acoustics team worked on site at the Miyoshi Civic Hall project, we saw only blue skies. Takatani Mountain stands near the center of the city and, apparently, between the month of September and early spring, the view from a top of the mountain resembles a sea of fog on all four sides. It’s said to be a truly fantastic view.
With the autumn-to-early-spring fog being a valuable tourist attraction for the city, it’s no wonder that Miyoshi City named its new civic hall “Kiriri”. “Kiri” means “fog” in Japanese. The new building’s facilities include a 1,006-seat Main Hall, a flat-floor, multipurpose Salon Hall that accommodates about 150 persons and 8 Studio spaces, plus support rooms.
Jun Aoki & Associates served as the project architect. Kajima Corporation and Katogumi Co., Ltd. teamed up in a joint venture to build the civic hall. Nagata Acoustics provided comprehensive acoustical consulting services on the project.
<< Unique Aspects of the Civic Hall’s Design >>
One of the unique aspects of this building’s design is that it was planned for use as an evacuation site in time of emergency due to floods. Miyoshi City’s Basen River runs near the site of the new civic hall and this river has a history of overflowing its banks. All of the building’s habitable spaces are built at a height of 5 m. (16.4 ft) above ground level.
Another unique aspect of the building’s design is its circulation system for the flow of people in the building. Typically, halls provide clearly separate circulation paths for performers and audiences. But the client and planners of Kiriri Hall wanted to plan for the many days when there are no performances on the calendar. On these days, the city wanted visitors to the building to have full access to all of the building’s rooms. For this requirement, the architectural team created one circulation path around the perimeter of the 1,006-seat hall. The architects also specified a set of doors where this hall’s wing connects to the studios’ wing so that the circulation path becomes temporarily interrupted when the doors are closed. With the doors closed, the space on one side of the doors becomes a green room for performers. When the doors are kept open, the same space functions as a space for meetings.
Miyoshi Civic Hall Plan
The building’s layout separates the wing with the hall and its perimeter corridor from the wing with studios and Salon Hall. The studios and Salon Hall are intended to double as spaces for small-scale concerts, lectures and exhibitions. This wing also includes office space for the civic hall’s operational staff.
This local—truly “civic”—hall does not make a nucleus of the larger hall’s space. Instead, the floor plan creates a user-friendly building for everyday use by the city’s residents.
<< Sound Isolation Design >>
The Main hall wing and studios wing of the building are structurally separated by the use of expansion joint. In addition, within the studios wing, while the studios are located in relatively close proximity to Salon Hall, we placed corridors between each of the studios and Salon Hall to avoid common walls between these spaces. The layout of the studios wing increases the sound isolation performance characteristic of the rooms.
We designated Studio 1 for enhanced sound isolation design so that it can be used for practice and performances by rock bands and Japanese taiko drum clubs. To accomplish this we gave the floor of this studio an anti-vibration and sound isolating floating floor structural system that uses a antivibration rubber. We designed studios 2, 4 and 6 with sound isolation appropriate for use by ensembles and by electric instruments such as guitars and keyboards. To achieve this level of sound isolation we installed floating floors on glass-wool boards in each of these rooms.
By adopting these sound isolation layouts and designs, we achieved a high level of sound isolation between each of these rooms and between these rooms and the hall wing. Using the “D” from Japanese Industrial Standard, the sound isolation between each studio and between the studios wing and the hall wing measures D-85 or higher. (The higher the value, the better is the sound isolation.)
<< Main Hall Room Acoustics Design >>
Main Hall Interior
The residents of Miyoshi City specifically requested that the hall’s acoustics be appropriate for classical music performances. On any project, for us to design a hall with the kind of longer reverberation time suited to classical music, we need to be able to give the hall sufficiently large spatial volume. In the case of this project, the scale of the hall’s overall spatial volume is relatively small compared with the total number of audience seats. Therefore, to achieve the desired reverberation time, we began our design by planning to keep the amount of sound-absorbing surfaces to a minimum.
However, during the design process we discovered the possibility of echoes along a portion of the rear wall that generates sound reflections. Eliminating the echoes required a sound absorption strategy. We decided to install sound absorbing surfaces on the rear wall, but only above a height parallel to the height of the top of an average person’s head when seated in the last row of the hall. With this limited use of sound absorbing surfaces we achieved a sound reverberation time of 1.7 seconds (at 500 Hz, with the hall full and the orchestra shell in use). From the quantitative perspective, this sound reverberation time suits classical music performances very well. We also confirmed qualitatively with our own ears that the hall’s acoustics will meet the needs of classical music concerts with sound that fills the hall and without any negative echo phenomena.
<< Salon Hall Room Acoustics Design >>
Salon Hall Interior
Salon Hall has a simple, rectangular shape and two technical galleries around its perimeter below the ceiling. In addition to designing the space so that it can be adapted to a wide variety of uses, we gave significant attention in our design to creating a room configuration and interior finishing that will produce high quality acoustics for music concerts.
Salon Hall’s two technical galleries turn the black-finished, reinforced concrete frame of the room into both functional and attractive interior elements. In addition to designing the galleries to maximize their use for the lighting needs of events and performances, we took advantage of the galleries’ surfaces by angling them so that they promote sound reflections beneficial to the clarity of instruments and vocals during music concerts.
In small spaces it can be difficult to obtain the kind of sound reflections that produce fine quality acoustics. In Salon Hall we gave special consideration to our design of the ceiling and the angle of the first technical gallery’s side walls. Our attention to this design successfully resulted in ceiling and wall shapes that produce valuable sound reflections throughout the room. We located sound absorbing material on the walls of the second technical gallery and installed a retractable curtain along one of the shorter walls to enable adjustments to the room’s sound reverberation time.
Salon Hall’s room acoustics have both a fullness that is well-suited to the music of string instruments and clarity of sound that makes speech easy to hear and comprehend. With the room configured to its maximum seating capacity of 124 chairs and with the curtain retracted, the hall has a sound reverberation time of 1.4 seconds (calculated value at 500 Hz). The same configuration has a calculated sound reverberation time of 1.3 seconds with the sound-absorbing curtain deployed.
<< In Summary >>
In this article I presented an overview and highlights of Miyoshi City’s new civic hall. The project implemented a plan that meets the needs of the city’s residents, from the circulation path of people in the building to sound isolation performance design that enables simultaneous use of the various rooms. The Main Hall and Salon Hall both have excellent acoustics for music concerts and other performances and events.
I believe that Miyoshi City’s residents now have a facility they will find easy to use, easy to enjoy and easy to let into their hearts. I hope that the residents become attached to this building so that they will maintain it and use it for decades to come—even as the building ages—so that when I return to Kiriri Hall many years in the future, I will find it full of vibrant activity. This is the only remaining hope for I have for this project on which I’m glad I participated.
Kiriri Hall website is available in Japanese. http://www.kiriri.org/
Minato Park Shibaura Opens
By Akira Ono
<< Project Overview >>
Minato Park Shibaura Exterior
On December 22, 2014, after planning and development phases that included a significant revision in 2011, the new “Minato Park Shibaura” facility opened near the East Entrance of JR Tamachi Station in Tokyo. This complex houses the local Minato Ward municipal offices as well as a new, public sports center, and community services offices such as an agency that promotes gender equality and a consumer protection office. By placing the municipal (i.e. “ward”) administrative offices and the spacious flat-floored gyms under one roof, Minato Ward intends for the new building to also serve the community as an effective evacuation destination should there be a time of emergency.
NTT Facilities, Inc. served as the project architect. A joint venture of Kajima Corporation, Kinden Corporation, Tonetsu Corporation and Suga Co., Ltd. built the facility. Nagata Acoustics provided the acoustical consulting services.
The Park Shibaura project began as an urban renewal plan for the neighborhood north of the Tamachi JR Station East Entrance. The neighborhood had a site where a Tokyo Gas Co., Ltd. research facility previously stood and also had a Minato Ward branch administrative office and a sports center in separate locations. The project’s objective included redrawing the lines of the properties to enable a renewal project that would integrate the neighborhood’s municipal offices and indoor sports facilities into the Minato Park Shibaura building.
The project location is on the bay and port side of the JR railway tracks. (“Minato” means “port” in Japanese.) The revitalization of this area includes an already completed park planned by the Tokyo Metropolitan Government and a new building for Aiiku Hospital, which focuses on obstetrics and pediatrics. In addition, Tokyo Gas is collaborating with a major Japanese developer on a project with the working title “TGMM Shibaura Project” that will add two high-rise towers with commercial space, a hotel and other spaces to the area. The expected completion date of the TGMM Shibaura Project is 2019, in time for use during the next Tokyo Olympics.
There are also plans to improve the accessibility of JR Tamachi Station. Specifically, a barrier-free walkway above the street in front of the East Entrance will connect directly with both Minato Park Shibaura and Aiiku Hospital. The walkway will be completely enclosed to protect pedestrians from inclement weather. The plans also include making this walkway into a kind of mini shopping mall with some shops and restaurants.
<< The 2011 Revision of the Project’s Culture and Arts Wing >>
Originally, the Minato Park Shibaura Project—which mainly has Minato Ward offices and the sports center—was conceived as a complex with three wings: a wing with the main gymnasium as its main facility; a wing with the sub-gymnasium as its key space; and a Culture and Arts Wing with a 600-seat theatre and a concert hall. However, after the 2011 Great Tohoku Earthquake, Minato Ward reassessed its emergency and disaster readiness and made emergency preparedness its top budgetary priority. As a result, the Culture and Arts Wing of the project was stopped. Instead, its monetary resources were focused on tsunami and flood disaster preparedness.
The original design of the Culture and Arts Wing featured a wonderful, multi-floor layout with a mezzanine practice zone and a concert hall on the top floor that would have had an appropriately high ceiling for excellent acoustics. The high quality halls and rooms planned for the Culture and Arts Wing only made the cancellation of this part of the project that much more of a disappointment. Indeed, instead of simply taking the hall project out of Minato Ward’s future, the planners found an alternate site very near the bay at Hamamatsu-cho 2-Chome, 4 Chiku. Minato Ward’s planners now think this is an even better location for the culture and arts facility than the original Shibaura site and they say they will re-start the Culture and Arts Hall project there. The new location is the former site of World Trade Center Building which has been rebuilt elsewhere.
The Original 3-Wing Project Plan
The new project will have one 600-seat multipurpose hall with cutting edge, high quality performance space functionality and a room for rehearsals, practice and other uses that accommodates up to 100 people. The building will also have some smaller practice rooms. The residents of Minato Ward who longed for the Culture and Arts Wing will need to be patient and hope that the yet-to-start project in Hamamatsu-cho comes to fruition. The details of that plan still need to be defined and finalized, and the current target completion date is 2024.
<< Minato Park Shibaura Noise and Vibration Isolation Design >>
At Minato Park Shibaura, the municipal services and administrative offices, as well as community meeting rooms and the multipurpose Libra Hall are all located on the ground (first) and second floors—the lowest levels of the building except for the garage. The sports facilities are concentrated on the upper floors and, because sports activities generate considerable noise and vibration from the floor impact of athletes running and jumping, the project needed a noise and vibration isolation design and strategy to prevent activities on the building’s upper floors from disturbing the work and activities of people using the first and second floors.
Our basic design strategy implemented a rigid floor slab under the upper floors. In addition, we specified floating floor structural designs under specific upper floor spaces located directly above offices and meeting rooms. The swimming pool where there are diving boards is an example of a space where we applied this design. The flat-floored Libra Hall, which is located on the first floor, also needed a design strategy to isolate it from noise and vibration due to the impact of athletic activity on the floor above it. We installed an anti-vibration and sound-isolating ceiling in this space.
<< Room Acoustical Design of the Multipurpose Libra Hall >>
Cross-section views of Libra Hall
Libra Hall is a multipurpose hall with a flat floor and deployable stadium-style seating, The seating has variable configurations that make it possible to increase the amount of floor space in front of the first stadium-seating row so that persons in wheelchairs can easily join the audience and the flat floor at the front of the room also makes it easy for performers in wheelchairs to access this part of the hall. Easy accessibility for musicians in wheelchairs so that they can perform with their ensembles and choirs was a specific client requirement for this space.
When configured with its stadium seating, Libra Hall’s reverberation time measures 0.7 seconds at 500 Hz. With just four rows of stadium seating in use, the reverberation time increases to 0.9 seconds. These are appropriate reverberation times for the kinds of events planned for this multipurpose hall.
<< Room Acoustical Design of the Indoor Swimming Pool and Gymnasiums >>
Sports Center Indoor Pool
For the indoor swimming pool, we specified a membrane ceiling that could be expected to provide the appropriate sound absorbing characteristics. We dispersed the sections of membrane in a pattern across sections of the ceiling’s frame to achieve the desired sound absorption. We also used sound-absorbing surfaces for a portion of the upper side walls of the indoor pool’s space. The sound reverberation time in the space is about 2 seconds at 500 Hz.
The Japan Swimming Federation has set guidelines for the sound reverberation time of indoor pools. For Olympic pools, the guideline specifies that the reverberation time be less than 3 seconds. For other pools and in general the guideline specifies that the reverberation time be less than 4 seconds. Because reverberation time is proportional to the spatial volume of a room, using seconds as the defining guidelines only provides a rough indication that the sound level will be comfortable in a given situation. Nevertheless, using the guidelines as the reference, the controlled reverberation time we achieved at Minato Park Shibaura Pool well exceeds the level of quietness required to make the pool environment acoustically comfortable for swimmers and poolside visitors.
In the large spaces of the gym and sub-gym, we used as the guide for our acoustical objectives the standard measurement for rooms of 20-to-30% average sound absorption. Upon completion of the building, the gym’s average sound absorption measured 27% with a sound reverberation time of 2.1 seconds at 500 Hz, validating the salutary results of our acoustical design for this space.
The indoor pool, main gym and sub-gym are just three examples of the spaces at the sports center. There is a specialized space for most every popular indoor sport, including badminton courts and a table tennis gym, dojos for martial arts such as judo, kendo and kyudo, a floor with strength and aerobic training machines and equipment, and group exercise studios.
As other Shibaura revitalization projects complete the neighborhood around the East Entrance to Tamachi Station will continue to evolve with more housing, medical facilities, community services and facilities to support a healthy lifestyle. Minato Park Shibaura makes a positive contribution that residents of this neighborhood can start enjoying now.
The sports center’s website is available in Japanese. http://www.minatoku-sports.com/
Nagata Acoustics Inc.
Hongo Segawa Bldg. 3F, 2-35-10 Hongo
Bunkyo-ku, Tokyo 113-0033, Japan
Tel: +81-3-5800-2671, Fax: +81-3-5800-2672
1990 S. Bundy Drive, Suite 795
Los Angeles, CA 90025
Tel: +1-310-231-7878, Fax: +1-310-231-7816
75, avenue Parmentier
Tel: +33 (0)1 40 21 44 25, Fax: +33 (0)1 40 21 24 00