News 17-06 (No.354)
Issued : June 25, 2017
New Civic Center Opens in Kagawa Prefecture’s Kan-Onji City!
By Nobuhiko Hattori
Kan-Onji Civic Center Exterior
In April, 2017 a new civic center opened in Kan-Onji City, Kagawa Prefecture, on Japan’s Shikoku Island. In this article I will share highlights of the project and the new facility.
<< Location and Overview of Kan-Onji City Civic Center Project >>
The city of Kan-Onji faces west (towards Honshu Island) along the coast of Japan’s Inland Sea. It is the third largest town in Kagawa Prefecture, after Takamatsu City and Marugame City. The nearest train station to the new civic center is Kan-Onji Train Station, and from the train station to the banks of the Inland Sea is a mere 2 km. (about a 20-minute walk). Ibuki-Jima Island can be seen from the Inland Sea shore. Ferries take tourists and residents to small Ibuki-Jima Island at regular intervals throughout the day. In Japan, Ibuki-Jima is famous for its production of iriko, dried baby sardines that the people of Ibuki-Jima source from the Inland Sea waters and dry in the sun on nets. Iriko are an essential ingredient of the broth used for Sanuki Udon, a noodle dish featuring flat noodles that originated in Kagawa Prefecture.
Kan-Onji City’s first civic center was built in 1970, but that center became a worn and aging building by the end of the first decade of the present century. Starting in 2012, the city began work on plans for a new civic center. The new center completed and opened in April, 2017. Nikken Sekkei designed the new building’s architecture. A joint venture of Penta-Ocean Construction Co., Ltd and Fujita Koumuten Co., Ltd. built the facility. Nagata Acoustics participated as the acoustical consultant from the design phase through construction and conducted acoustical measuring at the completion of the project.
The new civic center uses land where an elementary school formerly stood. As part of the civic center project, the school’s gymnasium was renovated and made into a multipurpose hall. The new civic center’s Large and Small halls are arranged on two sides of the multipurpose hall.
The architectural design of the civic center building was inspired by imagery of the islands that rise gently above the surface of the Seto Inland Sea. From the outside, the building can be seen to have 3 wings that each rise to a different roof height. The wings that house the Large and Small halls have fly towers with different spatial volumes from each other and from the third wing of the building that houses the multipurpose hall converted from the school gymnasium. It’s easy to see how the imagery of Inland Sea islands led to the civic center building’s architectural design.
The building’s architecture is also notable for the eaves that encircle the building and the upper façade of custom-fabricated, 3-dimensional ribbed metal panels installed on the oblique angles of upper portions of the building’s exterior. The unique fly towers of the Large and Small halls are unlike the simple, vertical structures of most Japanese civic centers. Also, as explained below, the angled geometry of the exterior upper walls is repeated in the interiors walls of the hall audience seating areas and stages. Amidst the low-rise buildings of the neighborhood, the new civic center’s exterior adds distinctiveness without being overbearing.
<< Sound Isolation Planning and Design >>
First Floor Layout with Expansion Joint Locations Shown in Red
The functional and operational requirements of the civic center included the ability to use all of the spaces (the Large Hall, Small Hall, studios and multipurpose hall) simultaneously. To achieve this goal we developed a high-performance sound isolation design for the halls of the building. We began by locating the Large and Small halls as far from each other as possible and we added sound isolation elements to the structural design by using expansion joints to separate the halls’ foundational structures from other spaces.
We also gave consideration to sound isolation between the Large Hall and the 5 studios located at the rear of Large Hall’s lower level. In this area, we arranged the studios so that 2 of them have sound isolation and anti-vibration structural designs and we alternated these 2 studios with studios that do not have sound isolation structural elements.
Between the multipurpose hall and the Large and Small Halls, the existing building already had a plan to install expansion joints around its perimeter. We were able to repurpose these to provide sound isolation between the 2 spaces.
Our designs to isolate sound between the civic center's several spaces achieved the desired results. Using the Japan Industrial Standards Dr value for sound insulation between rooms we obtained Dr-80 between the multipurpose hall and the Large/Small Hall, and Dr-85 between the Large Hall and the Small Hall. (The larger the number, the better the sound insulation.) In particular, between the Large Hall and Small Hall, we achieved sound isolation for low frequency sound in excess of 80 dB. We attribute this excellent success to the combined implementation of physical separation of the spaces and the use of expansion joints.
<< Room Acoustics Design of the Large Hall >>
Large Hall Stage
Large Hall Main Audience Seating and Balcony
Detail of Large Hall's Exposed Concrete, Zigzag Side Walls
Small Hall Stage
Detail of Small Hall's Aji-Ishi Granite Masonry Side Walls
The Large Hall is a multipurpose hall with 1,200 seats. The hall has a main floor seating section and one balcony above the rear portion of the main seating. The stage is equipped with a sound reflection panel system that can be deployed and stored by rolling it along the floor of the stage to its position at the rear of the stage. We designed the system so that it can be set up to create stage depths of 12 m., 10 m., or 7 m. (39 ft, 33 ft or 23 ft) according to the needs of an ensemble’s configuration.
The interior finish of the Large Hall is mostly exposed concrete side walls with cedar framing and trim. To promote sound diffusion we specified that the side walls be built not as long, flat surfaces, but rather in sections angled in the vertical plane. We also were able to use the periodic groupings of 3 vertical posts installed for aesthetic reasons along both side walls to further enhance sound diffusion in the hall.
In addition to the sound diffusing elements, 2 m. (6 ft)-deep eaves encircle the entire seating area, installed at the same 12 m. (39 ft) height as the stage’s proscenium opening. Also, the details of the wall portions above the eaves and the ceiling may be masked from view because of the black paint used for these surfaces, but it is worth noting that the implementation of these wall portions follows the geometry of the exterior walls. For the angles of the wall and the ceiling, we provided specifications that enhance the room acoustics of the Large Hall.
<< Room Acoustics Design of the Small Hall >>
The Small Hall has 334 seats and is a small scale, multipurpose hall with a single bank of seating on a sloped floor. The programming for the hall envisions it being used for chamber music concerts, music recitals, lectures and similar events.
The distinguishing feature of this hall is clearly the use of rough masonry for its side walls and stage rear wall. This stone—locally sourced Aji-Ishi granite—is also used on ground-floor portions of the building exterior. The hall’s walls rise to a height of 11 m. (36 ft). Perhaps because of the angling of the walls, the combination of stone masonry and height feels comfortable and relaxed rather than confining.
The room acoustics benefit from the room’s basic configuration of walls that angle outward in the vertical plane as well as the intentionally uneven masonry and rough finish of the Aji-Ishi granite. These features appropriately soften the sound reflections from the walls and enable the weighty interior material to realize profoundly rich sound.
<< Mockups Aid in Accurately Constructing the Center's Unique Design Features >>
The Kan-Onji Civic Center project implemented multiple unique finishes that included the exposed, angled concrete walls of the Large Hall, the Aji-Ishi granite masonry of the Small Hall and the custom-fabricated, 3-dimensional metal panels on the upper portions of the building façade. When construction began, the hands-on field teams used a piece of land adjacent to the project’s on-site office to build mockups of each of these special finishing elements and reviewed the details of each of them with the architects, the general contractors and Nagata Acoustics. When all of the details were confirmed in the mockups, the construction workers built these elements of the building to accurately match the mockups.
The exposed concrete of the Large Hall began as a more complicated design from the architects. As the project participants together considered the concrete finish, fabrication details and acoustical effects of the various options, we adjusted to a more simple shape than the architect’s original conceptual design.
In considering the masonry mockup for the Small Hall’s walls, we needed to decide the size of the granite blocks and the how uneven the masonry installation should be. We confirmed that the implementation would create the appropriate-sized crevices between the pieces of granite so that the gaps between the blocks would not be too sound absorbing.
We also used the mockups of the exterior’s 3-dimensional, ribbed metal panels to determine and confirm noise mitigation strategies. In particular, we confirmed the need to implement a mitigation strategy for rainy weather conditions when rain falling on the roof generates noise.
<< Opening Concert >>
The civic center’s opening celebration concert was held in the Large Hall on April 1, 2017. Choirs and brass bands of local children performed the concert. In order to give as many children as possible the chance to perform on stage, the organizers had each group of performers take turns with other children by allowing each ensemble to perform just one musical composition and then let other children take the stage.
For both the children performing on stage and the families in the audience, the celebration concert surely will become fond memories. Another coming planned event to commemorate the center’s opening is a musical performed by members of the community. I look forward to hearing about many more performances and events that will be enjoyed by the residents of Kan-Onji in their 2 new distinctive halls.
The URL for Kan-Onji Civic Center: http://www.kanon-kaikan.jp
Renovated Utsunomiya City Cultural Hall Opens
By Kosuke Suzuki
Large Hall Stage
Large Hall Audience Seating Area
Small Hall Stage
Small Hall Audience Seating Area
On April 1, 2017, Utsunomiya City Cultural Hall opened its doors after the completion of a major renovation project. The original building was built in 1979 and has a 2,000-seat Large Hall and 500-seat Small Hall. The renovation project involved improvements and changes to both halls. The Large Hall has a proud tradition of offering one of the largest seating capacity in Japan’s North Kanto region with generous parking and equipment loading and unloading space. These features make Utsunomiya City Cultural Hall an especially desirable venue choice for brass band competitions and concert tours by popular music artists.
<< Scope of the Renovations >>
The renovation project began in 2014. In addition to addressing general wear and tear from years of use and improving barrier free access, the project’s major renovations aimed to bring the building’s spaces into compliance with revisions to Japan’s Building Standard Law enacted after the Great East Japan Earthquake of 2011. The law’s revisions require to prevent the possibility of a ceiling collapse in large venues. For the Utsunomiya project, the plans included not only seismic upgrades, but also other changes such as replacing all of the audience seating for better comfortability.
Because of the overall scope of the renovations, architects recognized the need for professional acoustic consulting participation in the project to guide the renovations in maintaining and—if possible—improving the two hall’s room acoustics. The design team hired Nagata Acoustics to participate in cooperation with the architects to achieve renovated halls with the desired acoustics.
A joint venture of AXS Satow, Inc. and Ando Architectural Design Office served as the architects for the project and a joint venture of Nakamura, Watanabe and Iwamura Construction were the general contractors. The building was closed from November, 2015 to March, 2017 while the renovation work was in progress.
<< Room Acoustics Designs for the Renovations >>
We began our work by measuring the acoustical properties of the original halls and interviewing the people responsible for the halls’ operations. We learned that both halls had been intentionally designed to control reverberations, considering most of performances hold at the halls would use sound amplification systems. Even though the halls had mobile orchestra shells, rather short reverberations in these halls resulted in insufficient acoustics for non-amplified performances.
Our investigation of the Large Hall’s acoustics (configured with the hall’s orchestra shell deployed) revealed a measured reverberation time of 1.6 seconds with average sound absorption coefficient of 0.26. The Small Hall’s measurement gave a reverberation time of 1.0 second with average sound absorption coefficient of 0.26. (The results are at 500 Hz in empty halls.) Compared with other multipurpose halls built more recently these values surely were insufficient for non-amplified performances.
To improve both halls’ appropriateness for non-amplified music performances, we developed plans to change the shape of the halls’ ceilings and install finishes with different acoustical properties than the finishes used in the original halls. For the shape of the ceilings we implemented a design that:
- Delivers sound reflections to the audience with a very short time delay from the generation of the direct sounds; and
- Delivers the reflections evenly to the entire audience seating area.
In selecting the halls’ interior finishes we chose materials that at least incrementally helped us lengthen the halls’ reverberation times. The changes we adopted for the interiors of both halls included:
- Removing portion of carpeting from the audience seating area floors; Kli>Replacing sound absorbers with sound-reflecting materials on the ceilings at the rear of the audience seating areas; and,
- Replacing the single layer gypsum board with a double layer of board for the ceilings above the audience seating areas.
<< Ceiling Design Improves Both Seismic Safety and Room Acoustics >>
Seismic safety was the first priority for the renovation designs of the halls' ceilings. For this goal, the original suspended ceilings were replaced with structurally rigid ceiling systems that enhance the seismic safety of the halls.
Qualitatively speaking, sound reflection characteristic of a surface increase with its weight. The new rigid ceiling raised the safety limit of the weight for ceiling finishes, so we chose to use double layer of boards instead of restoring the original single layer ceiling finish.
After the completion of the renovations, we measured the reverberation times and calculated average sound absorption coefficients in the Large and Small halls. In the Large Hall, we obtained 2.2 seconds for the reverberation time and 0.18 for the average sound absorption coefficient. In the Small Hall, we obtained 1.4 seconds for the reverberation time and 0.19 for the average sound absorption coefficient. (The conditions are the same as the original halls mentioned above.)
<< An Orchestral Celebration Concert Reopens the Large Hall >>
On April 1, Tokyo Philharmonic Orchestra performed in the Large Hall in a celebration concert for the reopening of Utsunomiya City Cultural Hall. I had the pleasure of attending the concert and confirmed with my own ears how the hall’s new acoustical environment enhances the enjoyment of the orchestra’s performance.
In the days and months after the celebration concert, the halls’ schedules have been filled with a diverse lineup of genres that are amplified and unamplified, include rock, popular music and enka concerts, rakugo storytelling and other events.
The concerts and events in the renovated halls are consistently receiving rave reviews. I send confident best wishes to Utsunomiya City Bunka Kaikan Cultural Hall for many future years as a popular and beloved community venue.
Radiant Heating and Cooling Systems
By Ryoichi Wada
Radiant Heating and Cooling Systems
I am currently working on a small, private space “salon” project that will use a radiant heating and cooling system. I visited the showroom of the proposed manufacturer of the system to experience and examine the system in operation. I was impressed by the comfortable and consistent temperature that the system delivers.
In recent years, the adoption of radiant heating and cooling systems in Japan has grown and expanded. Initially, the systems were predominantly used for small and medium-scale applications such as homes, local stores and offices. Now, they are also being installed in libraries with spacious reading rooms and spaces that are partially open or connected to an outdoor area. However, for larger indoor spaces—and especially for spaces such as halls and theatres with intermittent heating and cooling system operation patterns—the operational costs, special considerations for installation and efficiency calculations of radiant heating and cooling systems remain topics that impede adoption of these systems.
When selecting a heating and cooling system, it is important to consider not only whether the system provides an environment of comfortable and well-balanced temperature, but also whether the noise level generated by the system suits the room’s purpose and what strategies can be applied to reduce the heating and cooling system’s noise level to increase the quietness of the space. From an acoustical perspective, radiant heating and cooling systems offer some benefits, but there may also be disadvantages to consider. In the below paragraphs I enumerate and discuss some benefits and disadvantages of radiant heating and cooling systems.
<< The Main Difference between Radiant Systems and Central Systems >>
Most radiant heating and cooling systems use a medium that heats and cools metal panels. The heat of the panels transfers into the room or, in the case of cooling, the heat in the room transfers to the panels, resulting in adjustments to the temperature of the room.
Forced air central heating and cooling systems are the most prevalent installed systems. The main differentiator between radiant systems and central systems is that radiant heating and cooling systems do not require use of a supply fan to deliver heated or cooled air into the room. (For this discussion, I leave aside the question of how ventilation occurs.)
<< Benefits of Radiant Heating and Cooling Systems >>
For spaces with central heating and cooling systems, we develop strategies to reduce and mitigate the noise and vibration generated by the system’s supply fan. We also adopt measures to prevent noise and vibrations from related equipment both inside the system and external to it. In addition, we mitigate and prevent sound transfer and crosstalk phenomena through the system’s ductwork by implementing appropriate sound insulation and other measures.
Of course, implementing these strategies requires planning for the physical space that these elements require as part of the architectural design. For example, heating and cooling systems typically have several kinds of fans, including supply, ventilation and smoke control units. Spaces that use radiant heating and cooling systems may still need ventilation fans and smoke control units, but they eliminate the need for supply fans. In a central heating and cooling system, the supply fan and associated ductwork handle the largest amount of air and require considerable space.
Because radiant systems eliminate the need for a supply fan, these systems fit into more compact spaces than do central systems. The smaller footprint allows for more living space or for installing other kinds of appliances or equipment.
In particular, I can think of projects such as a small halls, worship spaces or recording studios where there are constraints on the overall size of the space combined with the need for a quiet environment. On these kinds of projects, it may be difficult to find sufficient space to mitigate and reduce the noise and vibration a central heating and cooling system would generate. Installing a radiant heating and cooling system offers the benefit of a space-saving solution for these kinds of projects.
<< Disadvantages of Radiant Heating and Cooling Systems >>
I will now discuss important possible disadvantages of a radiant heating and cooling system from the perspective of room acoustics and noise and vibration mitigation. In Japan, most manufacturers of radiant heating and cooling systems use metal (mostly aluminum) panels. Therefore, if a large volume sound occurs in an interior space that has metal radiant heating and cooling panels, precautions must be taken so that the metal parts of the system that touch each other do not rattle. The best precaution is to ensure that the metal parts cannot touch each other. Some manufacturers already add cushioning material to their products for this reason.
Another important consideration for radiant heating and cooling systems is the medium used to transfer heat. For example, if the medium is chilled water or heating water, air can mix with the water and cause noise that sounds like the whooshing sound of flowing water. The sound volume of the noise may be very small, but, nevertheless, if classical music concerts will be performed in the space, or the space will be used as a recording studio, the possibility of this noise and its negative impact should be considered.
Before selecting a radiant heating and cooling system, it is desirable to confirm the specifications of the specific system and learn what possible noises it might generate. Then, a determination can be made as to whether the room’s intended purpose allows for the noise levels that the radiant heating and cooling system may generate.
For the project I mentioned at the start of this article, we thoroughly investigated all aspects of the proposed radiant heating and cooling system prior to selecting and installing it. The project is still in progress, so I cannot yet confirm that the desired level of quiet has been achieved. Nevertheless, my visits to the manufacturer’s showroom gave me valuable insights and knowledge to consider for the decision-making process and I look forward to the project completion with confidence.
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