Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS


News 10-05 (No.269)

Issued : May 25, 2010

[ Japanese Version ]

Gero Synergy Center "Active" Opens in Gero Hot Springs Resort Town

by Fumiaki Sakamaki

Gero Synergy Center
Gero Synergy Center "Active" Exterior

Gero, a hot springs resort town in central Japan's Gifu Prefecture, has famous waters that well up from the Hida River basin. Banrishuku (a 15th century, Muromachi Era Buddhist monk and poet) and Hayashi Razan (the 17th century neo-Confucian philosopher and advisor to four Tokugawa shoguns) wrote that Japan possesses three great hot spring locations and included Gero as one of them. (The other two are Arima Hot Springs in Hyogo Prefecture and Kusatsu Hot Springs in Gunma Prefecture.)

Gero has a reputation throughout Japan as a picturesque and quintessential hot springs resort town. To reach Gero, the traveler can board the JR Takayama Honsen Special Express "Wide View Hida" train at its Nagoya Station terminus (in Aichi Prefecture) and ride directly to Gero. During the 1.5 hour ride to Gero, the traveler can enjoy magnificent vistas of the Hida River.

The Center's layout
The Center's layout

In March, 2010, the new Gero community center opened. (The formal name is Gero Synergy Center "Active".) The center features an 805-seat, multipurpose hall named "Izumi Hall" and an indoor sports arena, named "Hot Arena" that can be used for a wide variety of athletic competitions and can hold up to 2,900 persons. Sandwiched between these two anchoring facilities, the structure has a spacious and airy atrium named "Tanada Terrace" and, in separate locations around the atrium, there are seven rooms, called "dot pods". Each "dot pod" can be accessed from Tanada Terrace.

The "dot pod" rooms vary in size and each has a different designated purpose. Dot Pod No. 1 will be used for rehearsals and recitals and Dot Pod No. 7 has been acoustically designed as a practice room where large-sound-volume electric instruments can be played. The other five "dot pod" rooms also have designated purposes and provide space for specific activities and interests of Gero's residents. One "dot pod" room is a woodwork and metal crafts workshop, another is a Japanese tatami room and another room will be used for meetings.

The people of Gero gave the arena and the hall names that express their longing and expectations for the center and that truly make these facilities part of the hot springs resort town. They chose the name "Hot" for the arena and "Izumi", which means "fountain" or "spring", for the multipurpose hall.

Nihon Sekkei provided the architectural design and construction management services for the Gero Synergy Center project. A joint venture of Tsuchiya-gumi Co., Ltd. and Nissan Construction built the center.

<< The Center's Sound Isolation Design >>

For this project, we implemented the sound isolation design strategy of creating physical distance between the two main facilities (Izumi Hall and Hot Arena), which are located on the same level of the building. We accomplished this by locating the Tanada Terrace atrium between them.

Additionally, we gave special attention in our sound isolation design to isolating the large sound volumes expected to be generated in Dot Pod No. 1 (the multi-use studio, rehearsal and recital room) and Dot Pod No. 7 (the studio for electric instrument music practice). We designed these rooms to have anti-vibration and sound-isolating structures. For Dot Pod No. 1, we designed an anti-vibration floating sub-floor that uses a rubber material and a free-standing steel frame with extruded cement boards that create a sound-isolating layer for this room. For Dot Pod No. 7, we specified that the room be constructed as a concrete box entirely encased in anti-vibration rubber material. As a result, we secured the sound isolation between the Hall and the Arena up to 79dB and above. Between the Hall and Dot Pod No. 1 up to 97dB, and also with Dot Pod No. 7 up to 105 dB and above as well. (measured at 500 Hz in each case)

<< Hot Arena Room Acoustical Design >>

Hot Arena
Hot Arena

In a large indoor space such as the arena, the room's large spatial volume can cause the room's reverberation characteristic to be too long (too live). In this room, the wood wool cement board roof sheathing has been left exposed and provides some sound absorption. In addition, below the sheathing we placed glass wool board, with air space between this layer and the sheathing. We also added sound-absorbing materials and structures along most of the sidewall surfaces that are not windows.

<< Izumi Hall Room Acoustical Design >>

In designing the center's multipurpose hall, we took into consideration the considerable variety of purposes that the hall will serve for the Gero community. The hall will be used both for events performed by local residents and for concerts and other performances by visiting professionals. The genres of events will include classical music concerts, lectures, ceremonies and plays.

Izumi Hall (audience seating as seen from the stage)
Izumi Hall
(audience seating as seen from the stage)

Izumi Hall (with the stage sound reflection panels set up on stage)
Izumi Hall
(with the stage sound reflection panels
set up on stage)

Izumi Hall is a multipurpose hall with a balcony. We designed a stage sound reflection panel system for use during non-amplified music concerts and specified a height of 12 m. (39 ft) for the stage's proscenium opening in order to achieve continuity and a unitary acoustical space between the stage and the audience when the stage sound reflection panel system is set up on stage. The ceiling measures 15 m. (49 ft) above the stage floor and the main floor of the hall has a width of 18 m. (59 ft).

Some seats at the sides of the hall are located directly below the side balconies. The undersides of the side balconies form ceilings above these seats. Sounds that reflect off these ceiling surfaces reach the seats directly below too quickly. To mitigate this situation, we specified that the undersides of these balconies be built at a five degree downward angle toward the center of the first floor audience seating.

The ceiling lights above the audience seating area of a hall can be a source of uneven ceiling surfaces and gaps around the lighting fixtures that, in turn, cause gaps in the sound reflections propagated from the ceiling to the audience seating area. To prevent this problem from occurring, we designed Izumi Hall with an exposed pattern of catwalks above the audience seating area and attached the lighting to the catwalks. By using acoustically transparent expanded metal as the material to construct the catwalks, we ensured that the catwalks do not interfere in any way with the propagation and delivery of sound reflections from the ceiling to the audience. In addition to the room acoustical design advantages of the exposed catwalks, this design eliminated the need to add space for catwalks between the ceiling and the roof, enabling the architect to implement a desired overall lower building height.

For the hall's interior sidewalls, we wanted a material that would effectively reflect even low frequency sound, and we decided to use multiple plasterboard layers in order to achieve this objective. In addition, for the inner structure of the sidewalls of the main floor's audience seating area, we designed a system using mortar, concrete and wood ribbing that has both the necessary wall mass and provides excellent diffusion of sound reflections. The wood ribbing along the sidewalls is firmly fixed by the concrete behind it.

Izumi Hall's reverberation time measures 1.8 seconds when the stage sound reflection panel system is in use (at 500 Hz, in a fully occupied hall), a suitable reverberation time characteristic for a venue that will focus primarily on non-amplified music concerts. Likewise, my perceived sense of the hall's acoustics when I listen with my own ears is a hall with a wealth of low frequency tones and smooth, mellifluous acoustics.

<< Izumi Hall's Opening Concert and Hot Arena's Sporting Event Schedule >>

On Sunday, March 28, the Tokyo Philharmonic Symphony Orchestra performed Izumi Hall's gala opening concert. While I did not have the pleasure of attending this concert, I heard that the concert hall was filled to capacity and that the concert was a great success. Also, Hot Arena already enjoys a busy schedule of sporting events.

The residents of Gero Hot Springs have lost no time in quickly immersing themselves in the "fountain" of their new community center's Izumi Hall and the very active Hot Arena. I highly recommend a visit to this destination where you can enjoy the relaxation of the hot springs resort and replenish your energy at the new concert hall and sports arena.

For more information on the Gero Synergy Center, visit its Web site at http://www.gero-k.jp/



"Acoustical Building Materials from Around the World: Part 1 - "Sound Absorbing Glass"

By Dr. Keiji Oguchi

This article is the first of a series of articles I hope to write, from time to time, about newsworthy new building materials being developed in various places around the world. This time, I will discuss an acoustical building material from Switzerland. The material is "sound absorbing glass" or, more precisely, glass panels that have surfaces with many ultra-fine micro-slits that absorb sound using the same mechanism as the micro-perforated panels I wrote about in the Nagata Acoustics July, 2005 newsletter

Aula Hall
Aula Hall

A wall of Aula Hall (The white squares are FM glass.)
A wall of Aula Hall (The white squares are FM glass.)

Pressing on FM glass to test its resilience
Pressing on FM glass to test its resilience

During my travels and work outside of Japan, and especially when working on projects in Europe, I come in contact with sound absorbing building materials that are not available in Japan. What makes these ingenious materials fascinating is that they do not look like the kinds of materials one might expect to have strong sound absorbing characteristics. A number of these materials are being developed and manufactured in Switzerland. I went to Brugg AG and met with representatives of Akustik & Raum AG, the company that developed and manufactures "Fine-Micro Glass" (FM glass), an ultra-fine micro-perforated acoustic glass.

On the day I met with representatives of Akustik & Raum, I visited the Assembly Hall ("Aula Hall") at the University of Applied Sciences ("Fachhochschule Nordwestschweiz Hochschule f?r Technik"). The upper portions of this auditorium's four walls have 1,500 square pieces of FM glass (each piece measuring 20 cm. x 20 cm.) set into the walls. (The squares that look white in the accompanying photo are the pieces of FM glass.)

Behind each square of FM glass, the walls have a second layer of glass (that is not FM glass) and between each of the two layers of glass is a small amount of air space. The space between the two layers provides the sound-absorbing mechanism's "springiness", the micro-slits of the FM glass provide "mass" and the ultra-fine sides of the glass slices provide "friction", resulting in a resonator type sound-absorbing mechanism. The layer of glass behind the FM glass also provides sound isolation between the auditorium and adjoining spaces.

A piece of FM glass measuring 20 cm. x 20 cm., with micro-slits 0.2 mm. wide and spaced at 1.8 mm. intervals, has 100 micro-slits engraved on its surface. According to an Akustik & Raum representative, the company first tried to cut micro-perforations into glass, but was not successful with this approach. Instead, the company developed a method of using a high-pressure spray of sand and water to successfully produce the FM glass

The sides of the FM glass slices have a smoky-colored appearance that makes the glass look opaque when viewed obliquely. But when a person looks at FM glass while standing directly in front of it, the FM glass is transparent. When light pressure is applied to a piece of FM glass, for example by a person pressing with her thumb on the surface of the FM glass, the FM glass does not break; instead, it flexes. It was quite an unusual experience for me to experiment with touching and pressing on a piece of FM glass, because it was my first encounter with a glass having such resilient and pliable qualities.

Iwaki Alios Wins USITT 2010 Architecture Commission's Merit Award

by Toshiko Fukuchi

Readers of Nagata Acoustics newsletters have become well acquainted with Iwaki Performing Arts Center "Alios" through our articles in the May, 2008, June, 2008, August, 2009and April, 2010 issues. Recently, the Architecture Commission of the United States Institute for Theatre Technology (USITT) named Iwaki Alios a winner of its coveted Merit Award for 2010. On April 2, the project's lead architect, Mr. Naomi Sato, accepted the award at a ceremony held in Kansas City, Missouri.

The USITT twice previously conferred the Merit Award on Japanese projects. "Sai no Kuni" Saitama Arts Theatre won the award in 1996 and Setagaya Public Theatre won it in 1999, making Iwaki Alios the third Japanese theatre to earn the award.

Mr. Naomi Sato holding the award plaque and standing next to a poster about Iwaki Alios
Mr. Naomi Sato holding the award plaque and
standing next to a poster about Iwaki Alios



Iwaki Alios' first phase opened in April, 2008 and the performing arts center held its grand opening in May, 2009. The center has a large hall (1,705 seats), a mid-size theatre (500 to 687 seats), a small theatre (233 seats), two rehearsal rooms and four studios.

In selecting Iwaki Alios for the 2010 award, the USITT recognized, in particular, the innovative nature of both the design and operations of Iwaki Alios' large hall and mid-size theatre, as well as the way the wide, concourse-like corridors integrate the flow of people within the center and connect to the rehearsal rooms and studios.

Casals Hall's Last Day -- March 31, 2010

by Toshiko Fukuchi

On March 31, 2010, Nihon University's Casals Hall, in the Ochanomizu section of Tokyo, closed its doors and stopped all operations. The closure ended a 23-year-long history that began with the opening of the hall in 1987, funded by the sponsorship of Shufunotomo Publishing Company and with General Producer Haruhiko Hagimoto as the hall's creative guiding light. The hall quickly earned a reputation as a venue where many famous musicians and the most talented, up-and-coming musicians performed.

Casals Hall led the way with hall programming that was unprecedented in Japan, such as maintaining Japan's first resident quartet and producing an amateur chamber music festival. Casals Hall's many hall-sponsored programs and concerts wowed classical music fans and earned their well-deserved loyalty

The original design plans for the hall included installation of a pipe organ. In 1997, 10 years after the hall's opening, the addition of the pipe organ came to fruition. The graceful lines and ornamentation of the pipe organ built by organ builder J?rgen Ahrend matched architect Isozaki Arata's elegantly designed Casals Hall like the long-awaited marriage of two kindred souls. All of Japan's classical music world and, especially, organ music lovers praised Casals Hall's organ and acoustics.

Then, in the year 2000, Shufunotomo Publishing Company encountered economic woes, forcing it to end Casals Hall's hall-sponsored programming. In 2003, Nihon University acquired the entire Ochanomizu Square property from Shufunotomo Publishing Company, including Casals Hall. In the end, the university decided to cease all operations on March 31, 2010.

The concert performed on the hall's last day paid homage to the hall's namesake, Pablo Casals, and his dedication to teaching young musicians. When Casals Hall opened, Mr. Casals said he had agreed to the naming of the hall provided that the hall met one condition--a commitment to nurturing young musicians. At Casals Hall's last concert, on March 31, cellist Gen Yokosaka gave one of the two performances. Mr. Yokosaka first performed at Casals Hall in 2002, becoming the youngest cellist to perform on the Casals Hall stage. In addition to Mr. Yokosaka's performance, organist-in-residence Hitoshi Mizuno also performed, filling the hall one last time with the beautiful tones of J?rgen Ahrend's pipe organ. Mr. Yokosaka's vibrant performance and Mr. Mizuno's rich, evocative playing of the pipe organ drew long and enthusiastic applause from the audience. For their encore, Mr. Yokosaka played Pablo Casals' beloved "El Cant dels Ocells" ("Carol of the Birds"), undoubtedly bringing tears to the eyes of many people in the audience.

Future plans for this venue remain unclear. However, 23 years of outstanding classical music programming will clearly retain its value for posterity. Listening to "El Cant dels Ocells" on March 31, 2010 in Casals Hall, I surely was not alone in wishing that this hall may someday be brought back to life and again be sustained as Tokyo's premier chamber music concert hall.


Nagata Acoustics Inc.

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[ Japanese Version ]