Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 13-07 (No.307)

Issued : July 25, 2013

[ Japanese Version ]

Charles Bronfman Auditorium (Mann Auditorium) Reopens in Tel Aviv, Israel

By Yasuhisa Toyota

Mann Auditorium (Interior View)
Fig. 1 - Mann Auditorium (Interior View)

Bronfman Auditorium (Interior View)
Fig. 2 - Bronfman Auditorium (Interior View)
(Incomplete Stage Ceiling)

Room Shape (Before and After the Renovations)
Fig. 3 - Room Shape
(Before and After the Renovations)

Tel Aviv's Mann Auditorium, home to the world famous Israel Philharmonic Orchestra, reopened on May 25, 2013 after the completion of a renovation project aimed at improving the venue's acoustics. Plans to improve the Mann Auditorium's acoustics began more than a decade ago and made progress for a while, but the effort was stopped when UNESCO declared central Tel Aviv-including Mann Auditorium-a World Heritage Site in 2003. The UNESCO declaration required preservation of the building's exterior and interior, precluding changes to the look of the hall.

Given these constraints, the challenge posed to us by this project was how to improve the hall's acoustics without altering the building exterior and without fundamentally changing the interior's design. We received the request to work on this project in October, 2007 and developed a renovation plan that readers can see in the April, 2009 issue of the Nagata Acoustics Newsletter.

Our renovation design included three main changes to the auditorium interior:

  1. We replaced the metal ceiling with an acoustically transparent, expanded metal ceiling and created a higher, new acoustic ceiling above the expanded metal ceiling. Fig. 2 shows the expanded metal ceiling under construction above the stage and Fig. 3 shows a longitudinal-section of the renovated room shape. As a result of our changes to the ceiling, we increased the ceiling height above the stage from 10 m (33 ft) to 15 - 16 m (49 - 52 ft) and substantially increased the overall spatial volume of the auditorium.
  2. We added low, partial walls in the auditorium's main floor seating area to achieve sound reflections from these additional surfaces.
  3. We modified the angle of the auditorium's side walls to obtain effective sound reflections.

We timed the start of construction to coincide with the beginning of the orchestra's off season in August, 2011. We initially anticipated a project schedule of 14 months' duration and a planned completion date of October, 2012, at the start of a new concert season. However, the construction period encountered some delays and, as a result, the orchestra's first test rehearsal in the renovated auditorium took place in March, 2013 and the gala opening on May 25, 2013. Even at the gala opening, the portion of the new, acoustically transparent ceiling above the stage was not 100% complete, as shown in Fig. 2. The orchestra had made plans to hold its 2011 - 2012 subscription concerts at an alternate location and had not planned for the unexpected, but unavoidable extension of its temporary home into a second season. However, when this need became a reality, the orchestra managed to adapt and make arrangements to extend its temporary venue.

The renovated Charles Bronfman Auditorium gala opening concert took place in the middle of the Israel Philharmonic's concert season. The program featured Beethoven's Violin Concerto with violinist Itzhak Perlman as soloist, and Mahler's Fifth Symphony performed by the Israel Philharmonic Orchestra under the baton of lifetime Music Director Maestro Zubin Mehta.

Prior to the renovations, the hall's acoustics could be described in one word as "dry" and the audience seating felt distant from the stage acoustically. The renovation project totally transformed the hall's acoustics. Now the orchestra's presence on stage feels close to the audience and the entire interior of the hall gives the impression of having strong acoustics. Instead of being a "dry" space it has become a "lively" space.

Maestro Mehta and numerous of the orchestra's players commented that the hall's on-stage acoustics dramatically improved, and it is much easier for them to play in the hall. As the orchestra becomes accustomed to its renovated and improved home, we can look forward to further polished performances by this accomplished orchestra.

When the orchestra performed its test rehearsal in March, 2013 we measured the hall's reverberation time and found that we had achieved a reverberation time of 2.2 seconds at mid-range octaves (500 Hz - 2,000 Hz) in an empty hall. Based on this measurement, we calculated the reverberation time in a fully occupied hall to be 1.9 seconds. Prior to the renovation, the auditorium was reported to have a reverberation time of 1.55 seconds under fully occupied conditions (according to Leo Beranek's Concert Halls and Opera Houses: Music, Acoustics, and Architecture). These measurements validate the sense of more lively acoustics that we can hear experientially in the hall.

Philanthropist Charles Bronfman donated a large portion of the funds that enabled this project to be realized. In recognition of his contribution, the hall was renamed Charles Bronfman Auditorium.

Miyagino Ward Cultural Center Opens in Sendai City

By Fumiaki Sakamaki

Building Exterior
Building Exterior

Miyagino Ward Cultural Center opened last October in Sendai City. The center enjoys a convenient location just steps from Rikuzen-haranomachi Station, and this stop on the JR Senseki Line is only 10 minutes from Sendai Station, a major train hub. The center's planners chose this site so that the new center will easily become a cultural destination. On the other side of Rikuzen-haranomachi Station stands the ward's governmental office building where residents come for a myriad of administrative purposes. With the addition of the cultural center, the station takes on double the importance as place to come for civic needs and cultural events.

The Great East Japan Earthquake of March 11, 2011 occurred right in the middle of this project's construction. On the morning of March 11, the construction team poured concrete into forms, completing the work before the earthquake struck. The earthquake caused some of the concrete to leak out of the forms. The unanticipated tasks of concrete cleanup and removal became the necessary next work of the construction crew. A seismic review of the roof structural design was also added to the schedule. The additional work understandably and unavoidably added to the overall duration of construction. Perhaps because of these unexpected hurdles, the construction superintendent and project leads put forth incredible effort to successfully complete the project. As a result, Miyagino Ward changed from being one of the last administrative units in Sendai City without a cultural center to becoming a community with a brand-new, seismically sound, post-earthquake facility.

<< Overview of the Facility >>

The new facility has the 384-seat PaToNa Hall for music performances, the 198-seat PaToNa Theater for drama, a rehearsal room and music practice rooms for the performing arts. It also has meeting rooms, a Japanese tatami room and a gym available for use by local residents as well as Miyagino Ward Central Citizens Center, Miyagino Ward Information Center, Miyagino Library, and Haranomachi Children's Well-Being Center.

NTT Facilities, Inc. served as the project architect and construction manager. A joint venture of Kajima Corporation, Okuda Corporation and Abekazu Co., Ltd. was the general contractor for the project.

<< Sound Isolation Design of the Cultural Center >>

Having a convenient location near a train station also means that the nearby environment produces significant noise and vibration from passing trains. In the case of this project, a subway line runs below ground immediately adjacent to the cultural center building. Because of these conditions and based on the results of on-site investigation of the vibrations, we carefully evaluated the placement of the hall and each of the other rooms in the facility's layout to determine where anti-vibration and sound isolating structural designs would be required.

We determined that the exterior environmental conditions warranted implementing anti-vibration and sound isolating structural designs for the hall and the theater. In addition, to enable the rehearsal room and the music practice rooms to be used simultaneously, we also adopted anti-vibration and sound isolating structural designs for these rooms.

During our post-construction testing of the project's acoustical performance, we found that train noise could be slightly heard in the theater, but at a lower level than the noise produced by the theater's HVAC system. In the concert hall, we confirmed that the train noise level is not detectable at all, being reduced to a low level that cannot be heard by the human ear.

PaToNa Hall (seen from the audience seating area)
PaToNa Hall from the Audience Seating
PaToNa Hall (seen from the stage)
PaToNa Hall from the Stage
Side Walls of PaToNa Hall's Audience Seating Area
Side Wall of PaToNa Hall

PaToNa Theater
PaToNa Theater

<< Acoustical Room Design of PaToNa Hall >>

The 384-seat concert hall has a single, main audience seating area with a sloped floor. We designed this space primarily as a venue for small-scale music concerts, such as recitals and performances by chamber music ensembles.

The shape of the hall begins with a basically shoebox-style footprint. For the ceiling's design, however, we diverged from the classic shoebox configuration and instead designed a ceiling that is the most novel aspect of the hall's shape. The ceiling rises to its maximum height above the stage, where it measures 14.5 m (48 ft). Above the audience seating area, from the stage to the rear of the hall, the ceiling follows a gently downward sloping curve. By using this ceiling design, we were able to obtain a design that generates a large amount of comparatively late sound reflections, something that is very difficult to achieve in a small-scale hall.

The upper portions of the hall's side walls are covered with a series of convex-shaped surfaces. We specified the precise angle of each of these convex surfaces so that, together with the ceiling surface, they direct sound reflections evenly throughout the audience seating area. In addition, we designed the bottom surfaces of the convex shapes to also serve as sound reflecting surfaces. Early secondary reflections are effectively propagated along the convex shapes' bottom surfaces and the adjacent side walls. Also, for the lower portions of the side walls, we installed horizontal ribbing to promote dispersion of the sound reflections.

The completed concert hall has a 2.0-second reverberation time (at 500 Hz, in occupied hall). This reverberation time is somewhat long for this size hall and contributes to the hall's appealing acoustics. The hall is well suited for recitals and chamber ensemble performances.

<< PaToNa Theater >>

The cultural center's theater is a small-scale hall with 198 seats and acoustics designed primarily for drama performances. The theater can be configured either as a flat-floored space or with a stage curtain and proscenium. Also, the movable and storable audience seats can be set up in a variety of arrangements. The theater's design makes it a versatile space for a variety of theater arts productions.

The theater's footprint has a square shape. To prevent flutter echoes, we installed both horizontal ribbing and protruding, sound-diffusing design elements along the side walls of the audience seating areas.

<< Miyagino Ward Cultural Center's Opening Year >>

After last year's opening of Miyagino Ward Cultural Center, it became an often used venue for recitals and other performances by local residents. We wish the center many years of serving the community as its main destination for cultural events and activities. When you visit the Tohoku area, I hope you will have a chance to visit Miyagino Ward and its cultural center.

The website for the center is available only in Japanese.

Hachijo Island's New Government Office Building and Multipurpose Hall

By Nobuhiko Hattori

Building Exterior
Building Exterior

At a location in the Pacific Ocean about 290 km (180 miles) southwest of Tokyo, Japan's Izu Islands offer the tropical atmosphere of South Pacific resort destinations even though these islands are administratively part of the Greater Tokyo Area. With two non-active volcanoes (Mt. Hachijo Fuji and Mt. Mihara), palm-tree lined streets, resort hotels and single-story, traditional Japanese minka houses protected from the elements by windbreak forests and stone walls, Hachijo Island epitomizes the Izu Islands' environment. Recently, in addition to its resort island attractions, Hachijo Island has also been the site of a project to build a new government office building and multipurpose hall.

<< Project Overview >>

Prior to this project, the town of Hachijo-machi used a government office building built more than 50 years ago. The town wanted a new facility with a more user-friendly infrastructure and seismic improvements. The new structure adds a multipurpose hall with 462 seats and, in addition to the originally planned upgrades, gives the town a centrally-located public facility where residents can enjoy good times together. The building has also been designed to be an emergency evacuation destination in case of fire or other urgent situation.

Under clear blue skies and surrounded by tropical greenery, the white tile exterior of the project's new building shines dazzlingly in the Hachijo Island sun. The building's layout has an open-air center courtyard ringed by the government offices and the multipurpose hall, as well as a gallery space and rooms for small classes or meetings. Chiaki Arai Urban & Architecture Design served as the project architect and Takenaka Corporation was the general contractor. Nagata Acoustics participated as Acoustical Consultant.

<< Multipurpose Hall "Ojare" >>

A View of Ojare Hall from the Audience Seating
Ojare Hall from the Audience Seating

A View of Ojare Hall from the Stage
Ojare Hall from the Stage

"Ojare", the name given to the new multipurpose hall, means "please come in" in the local Hachijo Island dialect. The hall has an on-stage sound reflection panel system that rotates into place when needed, multiple satellite technical catwalks near the ceiling above the audience seating area and movable banks of tiered audience seating that have an enhanced design to prevent them from swaying underfoot when hall patrons walk along the rows to and from their seats.

Like most multipurpose halls, Ojare Hall's acoustics and sound reflection panel system make it configurable for both music concerts and theater performances. The hall's purposes go beyond these standard multipurpose functionalities to include use as a flat-floored event space and to provide an indoor evacuation destination in case of an emergency on the island. To configure the hall for flat-floored use, the tiered banks of audience seats can be stored behind the stage.

In addition to the many ways that the hall can be configured, the partition wall between the hall and its foyer can be removed to create a large space directly connected to the open-air courtyard. This indoor-outdoor space is especially suited to events such as the island's traditional summer festival.

Hachijo Island is known for its ocean views, sunny days and two volcanos. Ojare Hall's interior takes its inspiration from these defining aspects of the island. The two most striking aspects of the interior design are the concrete walls and ceiling skylights. The surface treatment of the concrete walls and the placement of openings create visual imagery that can be likened to the lava-layered floor of the nearby ocean. The multiple skylights bring natural light into the hall, bathing the hall with sunshine in similar fashion to the play of light on Hachijo Island's nearby ocean waters.

From the acoustical design perspective, in this kind of room with angled and multi-surfaced concrete walls, our design focused on using the on-stage sound reflection panel system and the protrusions and angles of the audience seating's side walls to maximize the sound reflections to the stage and the audience seating. In addition, we took care to prevent undesirable long path echoes.

To address the abundance of sound reflecting surfaces in this hall with all concrete walls, we mitigated the possibility of too strong sound reflections by specifying a textured finish for the concrete and by adding some protrusions and indentations on the surfaces of the walls. At the rear of the hall, where we especially needed to prevent long path echoes, we placed a number of sound absorbing elements made of perforated aluminum backed by glass wool. The design of these sound-absorbing elements matches the hall's lighting fixtures. We also installed sound-absorbing material in the cylindrical portions of the hall's skylights to prevent these shapes from causing resonances and also to keep noise external to the building from leaking into the hall.

The new facility is in a location near Hachijo Airport. During the development of our acoustical design for the hall we investigated whether airplane noise would negatively affect use of the hall. Based on our research and evaluations and the frequency of flights in and out of the airport, we specified the use of double-paned glass for the skylights.

Occupancy in the new government offices began in May and the hall will officially open in August of this year. With Hachijo Island just a short, one-hour flight from Tokyo, I encourage readers to consider a "concert and resort" vacation to Ojare Hall and Hachijo Island.

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

(LA Office)
2130 Sawtelle Blvd., Suite 308
Los Angeles, CA 90025, U.S.A.
Tel: +1-310-231-7878, Fax: +1-310-231-7816

(Paris Office)
75, avenue Parmentier
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 ]