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



Nagata Acoustics News 99-8（No.140）
Issued : August 25, 1999




Tokyo Bunka Kaikan: Part 1, The First 45 Years

by Dr. Minoru Nagata

Tokyo Bunka Kaikan has a worldwide reputation as Tokyo's most well-known location for the performance of classical music, opera, and dance. Built at the entrance to Ueno Park, just a few minutes' uphill walk from JR Ueno Station, the hall welcomed its first audiences in the spring of 1961 and quickly monopolized Tokyo's performing arts calendar. Tokyo's resident orchestras switched their season programs to the hall and, for decades, virtually every international performer and ensemble of note who performed in Tokyo did so at Bunka Kaikan. (The official English name of the hall is Tokyo Metropolitan Festival Hall, but so many international performers have used the hall that its Japanese name, Bunka Kaikan, became widely known in performing arts circles everywhere.)

In the nearly four decades since Bunka Kaikan opened, several other large music performance venues have sprouted in Tokyo: NHK Hall in 1972; Suntory Hall in 1986; Orchard Hall in 1990, Tokyo Geijutsu Theater in 1991, Takemitsu Memorial Hall and Sumida Triphony Hall in 1997. As a result, Tokyo's classical music performances are now dispersed around the city. Despite the appearance of newer halls, however, Tokyo Bunka Kaikan's unique acoustics enabled it to continue to hold its own, retaining its excellent reputation with both Japanese and international musicians, orchestras, and other ensembles.

Over the years, Bunka Kaikan underwent numerous renovations and the installation of more modern equipment and facilities. However, in fiscal 1998, Tokyo Bunka Kaikan closed down for 13 months for a major, (6 billion renewal construction project. In this article, I recount the acoustical planning for the original hall, and some of the issues and events that transpired during construction, as well as some of the changes that were implemented during the first 45 years. In a second article, below, Toshiko Fukuchi tells the story of the hall's just-completed extensive renewal project.

<< Farsighted Planning and a Dedicated Team Build the Original Hall >>

The planning for the original Bunka Kaikan dates back as far as June 1953, to the organization of the Music Center Establishment Proposal Committee. This committee brought together the corps of engineers and other professionals who would study the primary acoustical plans for Bunka Kaikan as well as resolve the various acoustical issues related to the hall's architectural design and construction. NHK Science & Technical Research Laboratories, where I worked, took responsibility for the acoustical plans, while the Tokyo Metropolitan Government Construction Bureau's Department of Building and Repairs addressed the architectural and construction-related acoustics issues. For the Building and Repairs Department to consider Bunka Kaikan's acoustical requirements and issues from the earliest stages of their structural planning and decision-making was atypical of construction projects of the time. Their inclusion of acoustics from the start is clear evidence of the team's farsightedness and decisive willingness to forge new ground.

Table 1:　Bunka Kaikan's facilities and configurations
In October 1956, the plans developed by the committee were adopted as a project to commemorate the 500th anniversary of the city of Tokyo, with the intended name of the hall to be Tokyo-to Kinen Bunka Kaikan (literally, "Tokyo City Memorial Cultural Hall"). Basically, these were the plans by which the Bunka Kaikan we all know came into being. Soon thereafter, the detailed architectural design work was awarded to Kunio Mayekawa Architect & Associates and the acoustical design engineering was entrusted to NHK Science & Technical Research Laboratories. The general contractor was Shimizu Corporation. Construction began in April 1958 and was completed in April 1961, at a total cost of \1.63 billion.

Table 1 summarizes the original Bunka Kaikan's facilities and configurations. The Small Hall that was originally planned as a congress room was never used for that purpose. To this day, it has always been used as a small performance hall.

<< Bunka Kaikan's Acoustical Design - A Pioneering Accomplishment >>

NHK Science & Technical Research Laboratories provided acoustical engineering expertise at every stage of the Bunka Kaikan project, from planning, architectural design and engineering, and construction management through the final measuring of the hall's acoustics. The Laboratories signed its contract for the project directly with the client, the Tokyo Metropolitan Government . The content of our work included the design of: noise and vibration controls; room acoustics; and the sound systems. Yasuo Makita, then a manager in the Laboratories' Architectural Acoustics Research Unit, served as the Project Lead for a team of engineers composed jointly of members of the Laboratories' Architectural Research and Sound System Research units.

Compared with all the progress in the field of acoustics since that time, in the 1950s our design methodology at the Laboratory was still charting what for us was unknown territory, nor did we have sufficient access to scholarly design research materials or reference works. Nevertheless, Tokyo Bunka Kaikan marks the first project on which we applied a systematic acoustical design approach. As such, its success established our methodology as the standard for the acoustical design of multipurpose halls in Japan in the second half of the 20th century. Moreover, the importance of using a systematic and comprehensive approach continued to gain increasing credibility beginning with our pioneering work on the Bunka Kaikan project.

The original acoustical design work can be divided into the three broad categories of: (1) noise and vibration control; (2) room acoustical design; and (3) sound system design.

(1) NOISE AND VIBRATION CONTROL ISSUES AND THEIR RESOLUTION

* CONTROLLING NOISE AND VIBRATION FROM A NEARBY RAILWAY.
Back in the late 1950s, when we were designing Bunka Kaikan, the primary source of external noise and vibration was the Joban freight line and other trains passing through the Ueno Station. In the very earliest stage of our design work we measured both the noise and vibration levels at the project site.

From our measurements, we learned that the sound level from train whistles was 100 dB when measured at a point 60m from the sound source. Vibration from the trains varied depending on the location and depth at which the measuring was done. In the location that equates approximately with the substructure of the main hall's stage, the vibration level measured 0.2-0.5 gal (at vibration acceleration levels of 86 dB-94 dB).

Analyzing our noise and vibration measurements, Mr. Makita realized that choosing the best building layout was essential to achieving excellent acoustics at Bunka Kaikan. He persuaded both the hall's client and the architect to his way of thinking. Six layout proposals (A, B, C, D, E, and F) were developed, as shown in Figure 1, and each was evaluated based on both architectural and acoustics requirements. After all the pros and cons were weighed, proposal E, which put Bunka Kaikan's Main Hall as distant from the train tracks as possible, was selected for implementation.

Fig.1　Layout proposals for the Main Hall


The downside of proposal E was that it sacrificed the Small Hall's noise control to the needs of the Main Hall. Some years later, during one of Bunka Kaikan's renovations, the exterior windows along the corridor behind the Small Hall's seating area were replaced to improve their sound isolation capability. The quietness of the Small Hall improved even more markedly, however, when the Joban Line stopped running freight trains. I am not sure of the exact date, but from the time the freight trains disappeared, through the present day, the Small Hall is no longer bothered by problems of external noise control.

* DESIGNING SOUND ISOLATING EXTERIOR WALLS AROUND THE MAIN HALL'S STAGE.
Given our measurement of 100 dB for the site's exterior noise level, we applied the M' curve, derived from the masking threshold level to the background noise level of a room, to calculate the level of sound isolation required for the main hall. In those days, the M' curve was the state-of-the-art acceptable noise level criteria for determining the acceptable noise level when addressing a significant exterior noise problem. As a result of our calculations, we decided to implement a floating sound isolation layer, both in the stage side walls and on the Main Hall's roof. The Bunka Kaikan project was the first time that we used a floating sound isolation structure introduced to a auditorium in our design, a technique that thereafter became a common solution to achieve sound isolation requirements.

* PREVENTING VENTILATION SYSTEM NOISE.
Using both the power level (PWL) of each ventilator and the acceptable noise criteria of NC-20, we calculated the required noise reduction and installed sound absorbing ducts to satisfy our noise reduction requirement. We also installed anti-vibration equipment to counteract vibration from the ventilation system's fans and pumps.

(2) ROOM ACOUSTICAL DESIGN

Fig. 2　The Main Hall
Forty-five years ago, when we planned the 2,300-seat Main Hall of Bunka Kaikan, the only written information available that addressed the challenges of such a large hall was the Haas's effect concerning the 50 ms limits of sound reflections.

The architect's proposed room configuration for the Main Hall had a hexagonal shape (plan view) surrounded by side walls sloped outwards at an angle of 6.5 degrees . Our first step was to plot the path that early reflections would follow across two dimensions. Later, we plotted the path of the early reflections across three-dimensional space. From the echo time patterns we worked to understand the characteristics of sound reflection in the proposed configuration. Based on our findings, we decided to install diffusion treatments or sound absorbing surfaces wherever reflections would come in contact with a surface at 50 ms or greater. Examples of the techniques we devised for sound diffusion are the tiered layers of bare wood that form the side walls near the front of the hall, and the fixed reflection panels we installed above the front of the stage and extending over the front rows of audience seating. For sound absorption, our most notable innovation was the use of ribbed paneling as a surface covering. The ribbed panels are of assorted both varied width and spaces. Bunka Kaikan was the first project for which we adopted this effective sound absorbing surface.

Regarding the early reflections, we relied heavily on using the early reflections from the ceiling, and we followed the standard design practice of the time by adding more layers of early reflections for seating that was more distant from the stage. Here we devised an innovative design that created convex curves in the ceiling's underside (i.e., the side visible to the audience). The ceiling is constructed of 50 mm-thick concrete poured at the site. In my opinion, the unique shape and construction of Bunka Kaikan's heavy ceiling deserve much of the credit for this hall's reputation for "warm" acoustics.

(3) SOUND SYSTEM DESIGN

In addition to the two major work efforts of noise and vibration control, and room acoustics design, we also selected the amplification speakers for the hall and determined their placement. The main speakers used were then state-of-the-art monitor speakers, specifically, Mitsubishi brand model 2S-305. We installed one each of these speakers at each diffusion-enhancing wood side wall and three speakers on the ceiling at the rear of the hall. We also installed 72 supplementary speakers on the ceilings above the balcony areas. The supplementary speakers were fitted with a magnetic-tape-style delay machine to adjust for time lags.

<< Historical Overview of Renovation Work >>

Over the years, the common objective of most of Bunka Kaikan's renovation work has been to improve the functionality of the Main Hall's stage for opera and ballet performances without damaging the acoustics of the hall. The dates of major renovations and a summary of the work performed is shown in Table 2.

Table 2: MAJOR RENOVATIONS OF BUNKA KAIKAN SINCE 1961
(all renovations refer to the Main Hall unless noted as "Small Hall.")

・1970：

* Opera lighting fixtures added to stage
* Side stage reflection panels adapted for storage in basement and storage space constructed
* Orchestra pit enlarged and its sound absorption added

・1978：

* Sprinklers added
* Lighting and sound system overhauled and updated

・1984：

* Absorption strata removed from Small Hall's rear wall (partial), stage rear wall, and ceiling
* Upper portion of corridor's stone wall balustrade removed

・1985：

* Audience seating replaced
* Rehearsal room C newly constructed on basement level

・1986：

* Small Hall audience seating replaced

・1999：

* All stage reflection panels replaced with single integrated unit with basement storage
* Ventilation system fully renovated
* Stage lighting, backstage apparatus and sound system upgraded
* Total renovation of backstage area and dressing rooms
* Redesign of lobby interior
* Construction of additional rest room facilities


<< Bunka Kaikan's Acoustics >>

From its opening day in 1961, Bunka Kaikan has maintained a steady reputation among Tokyo's orchestras, visiting international orchestras, and other performers for its "user-friendly" stage. Nevertheless, when Tokyo's orchestras first moved their season concerts from Hibiya Kokaido to the new Bunka Kaikan Main Hall, the press reported certain complaints expressed by some orchestra players. When Suntory Hall opened, more than two decades later, similar complaints arose from the ranks of Tokyo's orchestra players about the on-stage acoustics. Yet, as time passed, both players and audiences became accustomed to the brilliant, rich sound of Suntory Hall, acoustics that epitomize the characteristics of fine contemporary halls.

Fig. 3　Reverberation time of the Main Hall
By comparison with such recent halls, Bunka Kaikan's Main Hall sounds more somber and has less brilliance. Bunka Kaikan was built this way so that it would be suitable for the staging of operas as well as the performance of concerts. What it lacks in brilliance, however, the Main Hall more than makes up for with acoustics that have a warmth and depth not experienced in other halls. In my opinion, this special characteristic results from the heavy convex curves of the ceiling, and the diffusion treatments of the stage space. Bunka Kaikan's Main Hall definitely continues to command a loyal following among music fans and performers who cherish the hall's distinctive acoustics.

In the process of understanding a concert hall's acoustical characteristics, different performance genres and playing techniques can emphasize and highlight characteristics that might otherwise remain unnoticed or unappreciated. I would suggest, however, that the passage of time and comparisons with other halls also help to define the unique profile of each concert hall.

Today, more than ever, no hall profile is considered complete without a reference to reverberation time. In closing, I present Figure 3, which shows how the Main Hall's reverberation time has changed from 1961 to the renovation of 1999.

Tokyo Bunka Kaikan: Part 2, Reopening Anew in 1999

by Toshiko Fukuchi

After closing for renovations in April 1998, Tokyo Bunka Kaikan celebrated its "Renewal Opening" in May 1999. Since its 16th year in operation, Bunka Kaikan had undergone some renovation every summer. But the scale and scope of the renovations accomplished during the recent 13-month closure were unprecedented. Five areas were targeted for renovation: (1) the Main Hall's stage; (2) the dressing rooms; (3) the audience and the lobby; (4) the building exterior; and, (5) seismic retrofitting. Renovation construction work began in October 1997, before the hall was closed, and was completed in March 1999, a period of 18 months. Such a major renewal undertaking could well be named the Grand Finale Renewal of the Century! The renewal architect was Maekawa Associates, Architects & Engineers. The general contractor was Shimizu Corporation.

<< Stage Renovations >>

Two aspects of the stage renovation were the most challenging and prominent: those involving replacing the stage's fly tower and the renovation of the reflection panels. The catwalks had deteriorated structurally and required reinforcement. A full 6m of the catwalk framework was removed and re-hung on a new steel framework covered on the exterior with a mixture of PC board and light concrete. This renovation required a major work effort.

The reflection panel renovation also required major physical construction work. Prior to the renovations, the reflection panels divided into a rear wall piece that could be retracted behind the stage, side panels that were stored in the hall basement, and suspended ceiling panels overhead. Post renovation, the reflection panel is now a single integral unit, all of which can be retracted below the stage. To accomplish this change, an 8m-deep storage space needed to be dug in the hall's basement. Thanks to this two-faceted major renovation, the stage has markedly improved weight and space capacities for hanging props and lighting. It has become an even more attractive venue than before for the staging of opera and dance performances, and is sure to spark the a new round of creativity in set design.

<< Preserving Bunka Kaikan's Unique Acoustics >>

Tokyo Bunka Kaikan's acoustics have always enjoyed a strong following of diehard fans among Japanese and international musicians, domestic audiences and visitors from abroad. So whenever the Main Hall has undergone a renovation that might affect the hall's acoustics--such as changing the audience seats--our goal was always to change the acoustics as little as possible, and to ensure that whatever changes did occur were only positive ones.

During the most recent renovation, as well, we used the same conservative approach. For any part of the renovation that might affect the acoustics, we focused on not making changes. The shape of the reflection panels and their material, the stage floor material and its construction, all of these we kept the same. The only deliberate acoustical change we made was to affix a layer of board behind the perforated wall at the rear of the Main Hall's audience seating. We made this change to lengthen the reverberation time of the middle and upper ranges.

<< Improving the Main Hall's Quietness >>

Another improvement we accomplished during this renovation was reducing noise from the Main Hall's ventilation system which had been minimally louder than the ideal for a concert hall. We had a new air chamber built beneath the main floor of audience seating and improved both the functionality and the quietness of the ventilation system. Adjustments are still ongoing with the goal of achieving a noise criteria of NC-20.

<< An Inviting and Comfortable New Look for the Entrance Hall >>

Another part of the major renovation was the interior entrance hall's total face-lift. A shop with music-related books and other merchandise and a flower shop (for all those bouquets Japanese audiences love to give performers!) were added, as well as relaxing chairs for those who want to sit and people watch during intermission. In contrast to the almost dark and institutional look of the old interior, the new entrance hall is bright and festive. The impact of the new interior on visitors to the hall is obvious. Where before the lobby was always quiet and seemingly devoid of people, now people come and go, linger, and use it as a place to gather. The Main Hall's lobby has more chairs and the refreshment counter has been newly placed in the lobby's center, making intermissions a more satisfying interlude. Couples meander on the building's terrace, gaze at the enticingly lit Western Art Museum nearby, and toast each other with glasses of wine. Instead of the old gray Bunka Kaikan, the hall is now an elegant and top-class place to bring a date! If you haven't been to Bunka Kaikan for a while, now is definitely a good time for you to renew your acquaintance.

For a detailed account of the Bunka Kaikan Renovation project, please see the publication of the Theater and Performance Space Technicians' Association, JATET, issue No. 33, where there is an article by Mr. Shima of Maekawa Associates, Architects & Engineers, the project architect (available in Japanese only).

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Nagata Acoustics News 99-8（No.140）
Issued : August 25, 1999

Nagata Acoustics Inc.

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