Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS


News 11-08 (No.284)

Issued : August 25, 2011

[ Japanese Version ]

Kokufu Community Center's Sakura Hall Opens

By Chiaki Ishiwata

Kokufu Cultural Center
Kokufu Cultural Center

On July 1, 2011, in Gifu Prefecture's Takayama City, the new Kokufu Community Center's Sakura Hall opened on a convenient site across from Hida Kokufu Train Station. In addition to Sakura Hall, the new community center's facilities include a branch of the city's municipal offices, a library and 5 rooms of various sizes for community center activities.

<<Sakura Hall Project Overview >>

Sakura Hall has a sloped main floor for audience seating and accommodates 600 persons. Our acoustical design prioritized the use of the hall for music performances. In addition to being suited to music programming, the stage can be reconfigured for symposia and ceremonies by rotating the stage side walls 90 degrees so that the spaces behind them can be used as stage wings.

Takayama City, the project's sponsor, specified the priority of acoustics for unamplified music performances as the primary goal of this hall. The city wanted to functionally distinguish the new venue from the already existing small hall of Takayama City's municipal cultural center building.

Stage of Sakura Hall
Stage of Sakura Hall

<<Partnering with the Local Architect>>

Abu Design created the architectural design for Sakura Hall and Hida Kensetsu served as the general contractor. Both of these companies are based locally in Takayama. Sakura Hall was Abu Design's first hall project. Three years ago, in 2008, Abu Design contacted us and asked us to participate with them on the project.

We began our consulting for this project by talking with Abu Design about some important fundamental concepts. About the effect of early sound reflections on room acoustics and how a room's shape and dimensions play a critical role because these aspects of the space govern the propagation of the early sound reflections. We also discussed the importance to the hall's acoustics of non-architectural, building system design decisions, such as reducing and abating HVAC noise and determining the location of air vents.

Sidewalls of the audience area
Sidewalls of the audience area of Sakura Hall


After our basic discussions, we prepared 2-dimensional and, then, 3-dimensional computer simulations of proposed ceiling and wall dimensions and the proposed slope of each of these surfaces. We analyzed the simulations and provided advice on these specifications as the architect developed Sakura Hall's design. In a blog posting, one of Abu Design's architects reminisced about this period, writing, "We could not simply approve 'as is' the hall shape they [Nagata Acoustics] first specified, and this led to considerable back-and-forth negotiations. The lattice design of the hall's rear wall is one example of the results of these negotiations." Remembering those discussions and negotiations after the hall's successful completion makes me nostalgic for the energetic and friendly debates of our collaboration with Abu Design.

<< Spacious Acoustics and Beautiful Woodworking >>

Even though Sakura Hall is small in overall size, it manages to have a spatial volume of 5,800 cu. m. (204,825 cu. ft) and a 12 m. (39 ft) ceiling, creating a venue with spacious acoustics.

Audience seating area of Sakura Hall
Audience seating area of Sakura Hall


Also, a distinguishing characteristic of this hall is the incredible craftsmanship of the wood portions of the audience seatbacks and the seats' armrests, which are each crafted from pieces of solid wood. The local Hida Woodworking Federation and seating manufacturer Kotobuki Corporation collaborated on the hall's seating. Hida area's long-tradition of skilled woodworking is wonderfully demonstrated in the seats' fine workmanship. The graceful curves of the armrests defy description in a beautiful melding of human skill and natural solid wood.

<< Sakura Hall's Inaugural Concert >>

On July 9, 2011, Kiyoshi Shomura (guitar) and Ken Nishikiori (tenor) performed in Sakura Hall for the hall's inaugural concert. On opening day, before the hall's doors opened, there was a long line of would-be audience patrons in front of Sakura Hall waiting for concert. At the start of the concert, almost every seat in the hall was taken.

When the two musicians came on stage the hall erupted into applause from the audience and I breathed a sigh of relief and satisfaction as I listened to the hall's strong and pleasant sound. The guitar and tenor ensemble performed beautifully and, in-between pieces, Mr. Shomura and Mr. Nishikiori added to the program's enjoyment by giving brief, entertaining talks that drew laughter from the audience and lightened the atmosphere.

<< The Local Architect Gives the Hall's Acoustics High Marks >>

After the inaugural concert, Abu Design's lead project architect, Tomohide Kurimoto wrote me an e-mail in which he said, "Of course, I expected that louder sounds would be audible throughout the auditorium. But when I sat in a seat of the last row and I could hear even the quietest notes, it nearly gave me goose bumps." I was truly happy to learn that this project's architect reacted in such a profound and positive way to his first experience of the fine acoustics that we helped him achieve.

Sakura Hall will mostly be used for performances by local residents, such as amateur piano recitals and choral concerts. Classical music concerts like the hall's inaugural event, featuring professional musicians may be calendared less often. Regardless of whether Sakura Hall's performers be professionals or amateurs, I hope this new hall will continue to hear the applause and laughter of Kokufu audiences for many years to come.


Toyota City's New Sports Facility-"Sky Hall Toyota"

By Makoto Ino

Sky Hall Toyota
Sky Hall Toyota

Toyota City's new sports and recreation destination facility, named Sky Hall Toyota, completed in October, 2010. In this home city of Toyota Motor Corporation, the residents have a concert hall, a Noh theatre, a community cultural center and an arts museum. And they also have a state-of-the-art soccer stadium, each area's gymnasium and swimming pools.

<<Project Completion in Two Phases >>

The Main Arena of the sports facility is housed in the building seen at the left in the accompanying photo. This building began construction in 2004 and completed in 2007. At the time, an older facility stood at its right side. When the Main Arena completed, it was immediately put into operation alongside the old facility. Then the old sports facility was torn down and the new martial arts Budokan and Sub Arena were constructed on the same site, housed in the building seen at the right in the photo. The project also included new parking accommodations. In autumn, 2010, with all construction finished, the entire sports facility building program became complete.

MHS Planners Architects and Engineers served as the project architect and overall project manager. Nagata Acoustics participated on the project for 6 years as the acoustical consultant. Our work included room acoustical design, sound system design, management of our design's implementation and acoustical evaluations and measuring.

Main Arena
Main Arena

<<The Sports Facility's Main Arena >>

The Main Arena building has four basketball courts' Main Arena at its center and various kinds of training and meeting rooms around the perimeter of the arena. For international sports competitions, the center arena has a surface area of 45 m. ~ 80 m. (148 ft x 262 ft), and a total of 3,470 audience viewing seats arranged on all four sides. The Main Arena also has temporary seating that can be added to the fixed seating, bringing the maximum audience seating capacity up to 6,500 seats.

The Main Arena's ceiling has a gently curved, dome shape and an effective acoustical height of 24 m. (78 ft). In a large space such as this one, delayed reflections from the walls and ceiling can cause long path echoes that impair clarity of the spoken word, making calls voiced from the playing field and speech amplified through loudspeakers difficult to comprehend. In addition, in this facility, we determined the need for a mitigating acoustical design strategy to prevent the otherwise likely occurrence of undesirable, focusing-like recurring sound reflections bouncing between the curved ceiling and the wooden floor.

To prevent the undesirable focusing-like phenomena, we specified glass wool as the finishing material for the entire ceiling, ribbed wood for the lower portions of the walls and perforated panels backed by glass wool for the upper portions of the walls. This design strategy aimed to maximize the Main Arena's sound-absorbing surface area. By implementing this design, we achieved a reverberation time of 2.8 seconds (at 500 Hz, with the hall unoccupied) and an average sound absorption coefficient of 0.28.

<<The Main Arena's Sound System >>

To obtain excellent sound clarity for the Main Arena's sound system, we concentrated the loudspeakers in a main cluster suspended at the center of the ceiling. In addition, we installed downward facing distributed speakers around the perimeter of the arena. Between these two kinds of speakers, we were able to install a sufficient number of units to fully cover the entire arena and to appropriately set the balance and delay of each unit.

Because our first priority for these loudspeakers was obtaining clarity of sound, we chose EAW's 3-way full-range coaxial AX series speakers for this project. These speakers maintain clear audibility across the spectrum of sound from low to high frequencies.

Sub Arena
Sub Arena

<< The Sub Arena and Budokan >>

The Sub Arena is used primarily by children and local groups for day-to-day sports and athletic activities. This space has two basketball courts and fixed seating for three sides of the gymnasium. The Budokan, which is located on the ground floor level of this building directly below the Sub Arena, is intended for kendo, judo and other martial arts competitions and trainings. The Budokan can be divided into three separate rooms to accommodate multiple simultaneous competition events.

The Sub Arena has skylights and walls with semi-transparent, fluororesin (Hydrophobic PTFE) surfaces. There are many glass windows at the lower walls. These design elements allow natural light into the room and give the room's interior bright, appealing feeling.

Similarly to our design for the Main Arena, we created sound absorbing surfaces in the Sub Arena by again specifying glass wool for the finishing material of this room's entire ceiling and glass-wool backed perforated panels for the walls. As a result, we controlled the arena's reverberations so that the Sub Arena's reverberation time measures 2.2 seconds (at 500 Hz, with the hall unoccupied) and the sound absorption coefficient of 0.27.

For this arena's sound system, we installed a simple sound system that uses two sets of line array loudspeakers. Amplified sound from the sound system can be heard clearly throughout the Sub Arena.

Anti-vibration floor structural support
Anti-vibration floor structural support

<< Noise Reduction for the Sub Arena >>

Because the Sub Arena will be used for various ball games and practice at the same time by many players, we anticipated that dribbling runs and similar movement in the arena will cause frequent impacts to the floor surface and generate loud noise volumes. Therefore, to prevent the activities in the Sub Arena from disturbing the people and activities in the Budokan martial arts rooms that are directly below the Sub Arena, we designed means to reduce the noise generated by these kinds of floor impacts.

Our noise reduction design began with a layer of anti-vibration material installed across the entire Sub Arena floor. Moreover we inserted pieces of thin rubber material in-between the metal floor joists at the point where the joists intersect. Finally, we filled the space between the floor and the substructure with layers of glass wool.

After the Sub Arena construction completed, we tested the results of our design by having 5 or 6 adults run and jump on the Sub Arena floors. In the Budokan rooms below no sound could be heard from the upper arena.

Also, I was pleased that at the time of completion this large project had zero acoustical issues. The sports facility now gives the people of Toyota City a place to enjoy both athletics and indoor spectator sports, complementing the city's excellent cultural, artistic and performing arts venues.

For more information about Sky Hall Toyota, contact Toyota City Amateur Sports Association, the organization that manages and operates the gymnasiums.


2011 Great Tohoku Earthquake and Theatres-the 18th Annual Aichi Prefecture Stage Technicians Seminar

By Makoto Ino

Almost four months to the day after Japan's enormous disastrous Great Tohoku (East Japan) Earthquake, the Aichi Prefectural Arts Foundation held the 18th Annual Aichi Prefecture Stage Technicians Seminar in the Aichi Prefectural Art Theatre's small hall. The main focus of this year's seminar was the earthquake's damage to theatres and halls in the Tohoku region and related relief and reconstruction efforts. I attended both days of the seminar (July 12 and 13) and will use this space to summarize what I learned.

<<Actions Being Taken by the Japanese National Government >>

The seminar began with Mr. Hirokazu Kadooka, Director of the Agency for Cultural Affairs' Office for Cultural Activities Promotion. Mr. Kadooka reported on the damage situation in the Tohoku region and measures being taken by the national government. His report included mention of funding that will start to be made available in August, 2011 to aid in dispatching artists to the disaster zones to promote cultural activities. Mr. Kadooka also mentioned that under the rubric of the Japanese cabinet's February, 2011 Third Culture and Arts Promotion Action Plan, a research committee is being established to consider systematic ways of supporting theatre, music and other performing arts and methods for grants and subsidies.

While the existing system of support for theatres has many ambiguous aspects to it, it seems that some tentative first steps have been made towards a concrete support plan. The Cultural Affairs' Office has posted its basic action plan and implementation schedule on a Japanese page of its Web site for all interested parties to read.

Ms. Izuna Tanaka's slide about England's disaster preparedness plans for theatres
Ms. Izuna Tanaka's slide about
England's disaster preparedness plans for theatres

<<England's Approach to Disaster Prevention and Relief for Theatre Venues >>

Next, theatre consultant Ms. Izuna Tanaka, who resides in England, spoke about that country's approach to crisis control and ensuring public safety. England bases its planning on three identified risk areas that might cause a disaster: fire, terrorism and floods. Recently, the possibility of data disappearing from personal computers or other data storage devices has been added as a fourth risk area.

For theatres, disasters can cause lost lives, suspended theatre performances and loss of or damage to physical theatre venues. As prevention measures, Ms. Tanaka presented a slide with the following list of disaster preparation plans implemented by English theatres.

  1. Understand the scope of current operational activities.
  2. Conduct risk assessments of the possible kinds of disasters that might occur.
  3. Strengthen the security management of physical facilities and create plans for reviving operations if a disaster should happen. These plans should include preparations for setting up a temporary office location, frequently backing up electronic data and having a plan for how to continue operations in the aftermath of a disaster.
  4. Upper management should do scenario training and be aware of the potential for a disaster to occur.
  5. Periodically review and update the disaster plan.

Ms. Tanaka also introduced us to England's Health and Safety at Work Act (HASAWA) and HASAWA's codified technical standards and operational regulations for work safety at entertainment venues. In my opinion, codifying these kinds of regulations needs to be included among the future developments and improvements in Japan's theatre-governing legislation.

<<Presentations by JATET Members from the Tohoku Region>>

In the third part of the seminar, the members of the Theatre and Entertainment Technology Association, Japan (JATET) reported on specific halls and specific building, stage machinery, lighting and operational damage resulting from the Great Tohoku Earthquake. By percentage, damage to stage machinery was estimated at about 20% of the region's total stage machinery and lighting and sound equipment damage was estimated to be only about 10% of the total value of equipment in the region.

However, in many halls and theatres, above the audience seating areas, the ceilings had board materials attached as finishing materials. In many of the venues with this kind of interior design, the earthquake caused these boards to come crashing down into the audience seating sections. We were all stunned and shocked to hear about this structural building problem. Correcting this structural issue in any hall or theatre with the problem deserves urgent attention.

<<The Still New Rias Hall becomes a Refuge for Evacuees >>

Ofunato Municipal Cultural Center (Rias Hall) opened just about two years ago in the Tohoku Region and we featured this project in our April, 2009 newsletter. At the seminar, a representative of the private company entrusted with Rias Hall's management (under the government's designated manager system) spoke in detail about the situation at this hall after the disaster.

Even though the hall was not designed or built to be an evacuation center, after the earthquake 450 people took refuge there and, as of July, 100 evacuees still remained. Hall employees cannot close the hall for maintenance and, in addition to needing to provide round-the-clock food and water, as well as restroom facilities, guarding around inside the hall, the hall has held more than 50 memorial concerts and other events for the disaster survivors.

For the Rias Hall project, the architect and the local residents held workshops to develop the hall's design and functionalities through a collaborative process. It seems to me that the building's locally-grounded, collaborative development process made the hall able to assume the unimaginable community-sustaining role it has played these past four months. The hall's employees and the evacuees have undoubtedly faced innumerable unforeseen hurdles. They have tackled each one of these problems together and together devised resolutions. The report about Rias Hall made me realize that the collaborative, on-site, local management and operational efforts of the residents of Ofunato epitomize the inner strength and community cooperation that will be the source of the Tohoku region's revitalization.


Nagata Acoustics Inc.

(Tokyo Office)
Hongo Segawa Bldg. 3F, 2-35-10 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.
Tel: +1-310-231-7878, Fax: +1-310-231-7816

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75011 Paris, France
Tel: +33 (0)1 40 21 44 25, Fax: +33 (0)1 40 21 24 00

E-mail: info@nagata.co.jp

[ Japanese Version ]