Title means "Quietness", "Comfortable Sound" and "Excellent Acoustics"

Nagata Acoustics News 02-4 (No.172)
Issued : April 25, 2002

Renovations and Acoustical Design - Part 2:
Hall Acoustical Renovations

by Keiji Oguchi

In this Part 2 of the article series begun in February, I will focus on renovations to the room acoustics of halls in Japan, with specific references to four halls.

<< Hall Acoustical Renovations Stay Unpublicized in Japan >>

A quick Internet search on the phrase "hall acoustic(al) renovation" produces a list of more than 800 websites. Most of these websites are the creation of U.S. companies and organizations. By comparison, an Internet search of the equivalent Japanese-language phrase produces only a handful of responses. It would be incorrect, however, to draw the conclusion that there are no acoustical renovations of Japanese halls. The lack of information on the Internet is merely due to the quiet approach most Japanese companies and Japanese halls take to accomplishing this work. The back numbers archive of Nagata Acoustics' News & Opinions includes just four issues with articles on renovations:

Issue #162 (June 2001) featured a comparison of acoustical renovations at Bunka Kaikan and Sun Plaza Hall.
Issue #140 (August 1999) featured two articles on Bunka Kaikan's major renovations of the large and small halls.
Issue # 128 (August 1998) discussed the renovation of Hatamachi Joho Bunka Center's Act Hall, and
issue #124 (April 1998)included a review of a visit to the renovated Chicago Orchestra Hall.

While we have completed other renovation projects as well, in the past, we chose other topics to share with our readers.

<< Two Main Categories of Hall Renovations >>

The purposes of hall renovations can generally be classified into one of two categories. Either the objective of the renovations is to upgrade a structural or functional aspect of the hall building, or the goal is primarily cosmetic. Examples of structural and functional upgrade objectives are seismic upgrades, and the installation of ramps, elevators and other apparatus to improve access for disabled persons. Also in this category are changes to the hall's acoustical, stage, or lighting equipment and capabilities to meet the requirements of new performance genres and artists. Cosmetic renovations aim to give a hall a new and refreshed "look" and to replace interior furnishings that are visibly worn or dirtied.

The most common acoustical elements of functional renovations are the installation or replacement of reflection panels and changes to the materials used for a hall's interior walls, seating, etc. Even if the renovations are solely for cosmetic objectives, the new audience seat coverings and other changes in materials used in the hall's interior can all have significant impact on the hall's room acoustics and, therefore, must be evaluated from the acoustical engineering perspective.

<< Tokyo Bunka Kaikan Recital Hall >>

Tokyo Bunka Kaikan is located in the Ueno section of downtown Tokyo. The recital hall has a seat count of 649 seats. The architectural design was the work of Mayekawa Associates, Architects & Engineers, which planned the hall for use as both a recital and for international symposia and conferences. A brochure that was printed when Bunka Kaikan was brand new shows an artist's rendition of the Bunka Kaikan recital hall configured with the kind of table setup used for an international symposium. However, according to a contemporary (1963, Vol. 15) acoustical report by the NHK Engineering and Research Group, the small hall's acoustical design team aimed to make the venue an appropriate location for use as a radio studio from which musical performances could be broadcast. For this purpose, a relatively short reverberation time was considered to be best. The NHK acousticians aimed for a short reverberation time and achieved their desired results of 1.4 seconds (as measured at the time in an unoccupied hall).

After Tokyo Bunka Kaikan opened, the recital hall was used almost exclusively as a recital hall. Recognizing this situation, in 1984, renovations were made to the hall to better match the hall's acoustics to the way it was actually being used. The accompanying illustration shows the primary changes implemented during this renovation.

A section of Tokyo Bunka Kaikan Recital Hall
<< Renovation Process for Bunka Kaikan's Recital Hall >>

In preparation for developing a renovation strategy for Bunka Kaikan's recital hall, we installed temporary reflection panels at the rear wall behind the audience seating and on stage. In this temporary environment, we took numerous measurements and listened to many "test" performances. After Bunka Kaikan's initial opening in 1961, a panel of absorptive material had been installed at the rear of the recital hall's stage and carpeting had been added in the audience aisles. These interior changes had further shortened the hall's reverberation time below the 1.4 seconds measured at the time of the hall's opening.

Based on our study of the recital hall's acoustics, we initially concluded that the best way to improve the hall would be to add reflective surface areas at each side of the stage, thereby strengthening the hall's lateral reflections. However, implementing this strategy would have impaired the sight lines between a portion of the audience and the stage and it would also have required major changes to the hall's interior architectural design. Instead, the client opted for our suggestion to implement renovations focused directly on lengthening the hall's reverberation time.

The 1984 renovations included the following:

(1) We removed the sound-absorbing material behind the stage.
(2) We replaced the sound absorbing, perforated ceiling panels with solid panels. (The perforated panels had been installed to attenuate reflecting sound back toward the stage.)
(3) We removed the sound-absorbing characteristic of the hall's rear wall by inserting wood strips over the existing sound-absorbing material that was visible in-between the rear wall's wood ribbing.

One of the lessons learned from the Tokyo Bunka Kaikan recital hall renovation project is the value of taking measurements and studying the hall through test performances and on-site listening before devising optimal and alternative strategies for ways to improve the acoustics. In addition, this project shows the importance of respecting the interior design of a hall when devising a renovation strategy, as the hall's interior is already well known to concert goers and they may have an emotional attachment to the original interior.

As shown in the accompanying graph, the 1984 Bunka Kaikan recital hall renovations lengthened the hall's reverberation time. Later renovations, particularly the recent renovations in 1999 have also maintained the hall's longer reverberation time.

Wood strips inserted between wood ribbing Reverberation time
<< Iida Cultural Center Renovation >>

Iida Cultural Center Hall seats 1,288 persons and was designed by the architectural firm of Takeo Sato. It is located in Iida City, Nagano Prefecture. One of the primary uses of this hall is as the main venue of the Affinis Summer Music Festival. The Affinis Festival brings together younger members of Japan's professional orchestras for a combination of seminars and concerts under the direction of noted international musicians.

Iida Cultural Center Hall is a standard multipurpose hall. For classical music concerts, the hall adds reflection panels suspended above and set at the sides of the stage.

For the festival's 10th anniversary season, in 1998, the Affinis Festival planners selected a program of compositions by Prokofiev and Tchaikovsky. The music required large configuration orchestras and the festival committee consulted Nagata Acoustics about renovating the hall's stage to accommodate the large-size orchestras required for the chosen program.

Nagata Acoustics performed an on-site investigation of the hall, which revealed two main concerns about the hall's reflection panels. One problem was that the side reflection panels were angled in such a way as to make the rear area of the stage exceedingly narrow. A second problem was that gaps were intentionally placed in-between pieces of the overhead suspension panels to allow room for the stage's suspension lights.

Our renovation strategy for Iida Cultural Center Hall took into consideration this project's tight budget constraints. We determined that it was most important to replace the overhead reflection panels and that the side reflection panels could continue to be used if their positioning was changed.

In the new overhead reflection panels we installed recessed lighting, enabling us to close the gaps between panels that were a negative aspect of the prior overhead reflection panel design. By re-positioning the side reflection panels at a considerably shallower angle, we both increased the available rear stage area and eliminated some gaps between these panels as well.

This hall's renovation improved the stage area despite several project constraints. One constraint was a weight limitation on the material that could be used for the ceiling reflection panels, due to the nature of the grid from which the panels are suspended. Because of the weight limitation, we were unable to use multi-layered laminated board for the ceiling reflection panels. Therefore, we designed each of the ceiling reflection panels with a convex shape in order to give them added rigidity.

Certainly, the most significant constraint of the project was its limited budget. Ideally, we would have preferred to install the ceiling reflection panels at a greater height above the stage. However, implementing this "ideal" strategy would have required replacing the stage's overhead grid as well as construction work on the stage's proscenium opening. Both of these activities were prohibitively expensive for this project.

Reflection panels
before(left) and after(right) renovation

<< Adding Above-stage Reflection Panels at Matsumoto Harmony Hall >>

Cloud-shaped reflection panels
Matsumoto Harmony Hall, located in Nagano Prefecture, has a seat count of 756 seats and the project architect was Nissoken Architects / Engineers. The hall has a pipe organ installed at the front of the hall, and it is the venue of the annual Saito Memorial Festival, which features small ensembles.

The organizers of the Saito Memorial Festival requested that overhead acoustic reflection panels be added to the concert hall because of the hall's high ceiling above the stage. The height of this hall's ceiling above the stage is 15.3 m. (50 ft). There are many halls with similarly high ceilings that do not have acoustic reflection panels above the stage. However, because the musicians who perform at the Saito Memorial Festival are in small ensembles, they are also seated far from the side and rear walls of the stage and this affects their experience on stage.

Our first step was to use inexpensive materials to test the affect of overhead, suspended reflection panels on how the musicians heard themselves while performing on the concert hall stage. We suspended cloud-shaped acoustic reflection panels made of plywood from one of the stage's special-effects battens and performed numerous listening tests. From the musicians who participated in our tests we elicited favorable comments about the ease of playing when the reflection panels were positioned 10 m. -- 12 m. (39 ft) above the stage floor. However, our tests also revealed individual preference variations among the musicians' responses.

When we perform on-site listening tests, we always conduct two kinds of tests: tests using objective acoustical measuring instruments and tests that use human participants. We tend to obtain little measurable variance for how sound waves react to changes in the suspension height of acoustic reflection panels, making the differences heard by the ears of our human participants all the more valuable.

Based on our test results, Nagata Acoustics designed a set of 12 transparent acoustic reflection panels. Each panel has surface dimensions of 1.5 m. x 0.9 m. (5 ft x 3 ft). The reflection panels are designed so that they can be installed during the Saito Memorial Festival and removed during the rest of the year, and this is how the Matsumoto Harmony Hall implemented their use.

<< Tokyo Bunka Kaikan Large Hall Renovation Project >>

Tokyo Bunka Kaikan's large hall has 2,303 seats and, like the recital hall discussed above, was architecturally designed by Mayekawa Associates, Architects & Engineers. This well-loved Tokyo hall has a decades' old reputation for the richness of its lower frequency sounds and the overall warmth of its acoustics. In March 1998, we began a major renovation of Tokyo Bunka Kaikan Large Hall. The number one requirement we were given on this project was "to not change Bunka Kaikan's distinctive acoustics!"

<< Goals of the Bunka Kaikan Large Hall Renovation >>

The Bunka Kaikan large hall renovation aimed to accomplish the following goals:

* Upgrade the hall's stage by
(1) replacing the suspending on-stage acoustical reflection panels with a single-unit orchestra shell that can be stored below the stage, in the hall's basement,
(2) replacing the stage's overhead grid, and
(3) installing state-of-the-art mechanical and electronic stage apparatus.

* Replace portions of the hall and hall equipment, such as the HVAC system, that showed deterioration or relied on outdated technology.

* Replace worn "cosmetic" aspects of the hall.

<< Strict Guidelines for the Acoustics-affecting Renovation Work >>

Before the hall's renovation work began, Nagata Acoustics determined which renovation work had a potential to affect the hall's acoustics. For all of this work, we required that the renovations strictly adhere to the hall's original specifications. For example, the structure of the on-stage acoustic reflection panels and of the stage floor mirrored the original specifications. The rather large opening between the top of the side wall reflection surfaces and the ceiling was also kept unchanged. Likewise, we followed exactly the original specification for the flies at the top of the stage side walls of the stage by not adding any absorptive finishing material to these areas, and we reproduced the ceiling above the audience exactly as it was prior to the renovation.

Sound absorption rate of the seats
In 1985, the large hall's seats had been replaced with a model upholstered with a vinyl-laminated cloth fabric for the front of each seat's back and having a solid, non-perforated material for the rear-facing part of the seats' backs. The 1985 change in seating materials also made every attempt to preserve Bunka Kaikan's special acoustics. For the 1999 renovation, the decision was made to replace only the upholstered portions of the audience seating. Even though this was a less drastic change than the seating replacement of 1985, we carefully measured the sound absorption characteristics of the old seating and made sure that the new upholstery preserves the same desired acoustical performance characteristics.

For more than 40 years since Bunka Kaikan first opened, this hall continues to be recognized as one of Tokyo's premier concert venues. It has sustained its excellent reputation because the people responsible for Bunka Kaikan's several renovations always put their heart and soul into their work. As an acoustician and as a music lover, I am sincerely grateful for the effort and passion they expended on this renovation project.

Ateliers Jean Nouvel and Nagata Acoustics Win Copenhagen Hall Competition

by Yasuhisa Toyota

The Danish Broadcasting Corporation recently announced the winning architect-acoustician team selected to design a major new concert hall to be built in Copenhagen, Denmark. The winning team is the French architectural firm Ateliers Jean Nouvel in combination with Nagata Acoustics as the acoustical consultants.

The decision to build a new concert hall at this time is related to the Danish Broadcasting Corporation's larger plan to move to a new campus. The concert hall will be built as a part of the corporation's new home. The new hall will have audience seating for 1,600 - 1,800 persons and will be designed as a concert hall. Plans call for the Danish National Radio Symphony Orchestra to become the resident orchestra of the new concert hall when it is complete.

<< The Many Kinds of Competitions >>

Each concert hall design competition uses its own selection process and methodology. Some competitions accept submissions from anyone who wishes to participate and some are by invitation only.

There are many opinions on the best method for selecting a concert hall's architect and acoustical consultant, and equally as many theories on what makes for the most successful combination of architect and acoustician. Sometimes the hall sponsor holds separate competitions for architect and for acoustical consultant, other times, the hall sponsor requests submissions from paired teams of architects and acousticians. In some cases, a competition is used to select the architect, while the sponsor selects the acoustical consultant without competitive bidding, and in other cases, after a competition is used to select the architect, the architect then, single-handedly, selects the project's acoustical consultant. Of course, there are still other selection methods as well. Each method has its strengths and weaknesses, which is why opinions on which methodology is best continue to be debated.

<< The Danish Broadcasting Corporation's Competition Process >>

For the Danish Broadcasting Corporation's international competition, the sponsor first created a short list of acoustical consultants. The selection committee also narrowed the participating architectural firms to a short list. Then, each of the architectural firms was asked to choose one of the short-listed acousticians as the architect's teammate. In the final round of the competition, each team of architect and acoustician submitted a joint proposal to the selection committee.

The competition selection committee selected the following eight acoustical firms to participate in the competition (listed in alphabetical order):

(1) Akustikon and Bo Mortensen Akustik;
(2) Arup Acoustics;
(3) Jaffe Holden Acoustics, Inc.;
(4) Ingemansson Technology, Jordan Akustik, Rindal Akustik;
(5) Marshall Day Acoustics Pty. Ltd.;
(6) Muller-BBM;
(7) Nagata Acoustics, Inc.;
(8) The Talaske Group, Inc.

Next, the competition selection committee chose eight architectural firms to participate in the competition. The committee named three architectural firms that it would invite to participate, and added five other architectural-firm participants selected from an open competition of written proposals.

The seven teams that submitted proposals in the final round of the competition were (in alphabetical order):

(1) Ateliers Jean Nouvel (F) + Nagata Acoustics, Inc. (Japan);
(2) Henning Larsens Tegnestue (DK) + Arup Acoustics (UK);
(3) Jose Rafael Moneo, Arquitecto (Spain) + Ingemansson Technology, Jordan Akustik, Rindel Akustik (S/DK);
(4) 3XNielsen A/S (DK)/ Knud Fladel and Nielsen (DK) + Akustikon and Bo Mortensen Akustik (DK);
(5) Rafael Vinoly Architects PC/ Aarhus Arkitekterne A/S (USA/DK) + Arup Acoustics (UK);
(6) Schmidt, Hammer & Lassen K/S (DK) + Akustikon and Bo Mortensen Akustik (S/DK);
(7) Snohetta A/S (N) + Arup Acoustics (UK)

<< Project Schedule >>

Together with Ateliers Jean Nouvel, we will now immediately begin work on the concert hall's design. Groundbreaking is scheduled for the second half of 2003, and the opening is scheduled in the autumn 2006. This is a tight project schedule. In particular, the short duration allotted for the design phase may be even more rigorous than the short design durations to which we are accustomed in Japan.

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Nagata Acoustics News 02-4(No.172)
Issued : April 25, 2002

Nagata Acoustics Inc.
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