Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 07-12 (No.240)

Issued : December 25, 2007

[ Japanese Version ]

Kansas City's New Concert Hall Specifications Tested in 1/10 Scale Model

by Kayo Kimotsuki-Kallas

Soon, the under-construction Kauffman Center for the Performing Arts (http://www.kcperformingartscenter.org) will redefine the cultural landscape of Kansas City, Missouri, a city famous for its many beautiful fountains and for the fine "Kansas beef" steaks that can be enjoyed in its restaurants. The new Center comprises a 1,600-seat concert hall that will be the home hall of the Kansas City Symphony, and a 1,800-seat proscenium-stage theater, primarily intended for ballet and opera performances. The Center's architect is Moshe Safdie and Associates (http://www.msafdie.com). Nagata Acoustics is the project's acoustical consultant, providing the entire range of services from acoustical design and related construction management to acoustical measuring and testing at the project's completion.

In the November, 2006 issue of this newsletter we shared an overview and news of the ground-breaking milestone of this project with our readers. In this article, I will focus my discussion on the two rounds of testing performed in the 1/10 scale model we built for the project. The scale model testing took place last winter and again in the summer of 2007.

<< The Hall's Shape, the Design in the Details and the 1/10 Scale Model >>

Plan View of KCPA Concert Hall
Plan View of KCPA Concert Hall

3D Cross-section View of KCPA Concert Hall (Courtesy of Moshe Safdie and Associates)
3D Cross-section View of
KCPA Concert Hall
(Courtesy of Moshe Safdie and Associates)

The seating of the Kauffman Center's concert hall surrounds the stage in a vineyard configuration. As shown in the plan and 3D cross-section views of the hall that accompany this article, the hall's footprint has an oval shape and the front wall of the hall forms a sweeping arc in the vertical direction. Overall, the hall's interior architectural design includes many concave surfaces.

While concave surfaces figure prominently in the hall's architectural design, from an acoustical perspective, the use of concave surfaces is always approached with caution because they unfortunately raise concerns about undesirable sound focusing and echo phenomena. In order to maintain the integrity of the architect's concave design, we prevented sound focusing problems by using latticework and metal mesh materials with a large percentage of open area for the front wall's concave surface, building sound diffusing elements behind the mesh wall. In addition, we specified precisely determined angles for the sidewalls of the hall so that they function as effective sound reflecting surfaces, proactively incorporating sound diffusing elements that visually blend well with the hall's architectural design. Throughout the room interior, in every detail of the design, we successfully emphasized and implemented the acoustical design needs of this concert hall.

Keeping all of these carefully devised detailed plans in mind, in the 1/10 scale model we aimed to reproduce as faithfully as possible all of the acoustical design specifications of the actual concert hall. To achieve this end, we adapted our choice of materials and used creative scale-model building techniques. To the eye, the scale model appears to be constructed with elaborate detail and precision. Even the architect's and general contractor's project managers found that the scale model aided them greatly in understanding the hall's configuration.

<< Testing in the 1/10 Scale Model >>

1/10 Scale Model of KCPA Concert Hall

1/10 Scale Model of KCPA Concert Hall
1/10 Scale Model of KCPA Concert Hall

Prior to performing tests in the 1/10 scale model, we scrutinized the design for the hall's configuration using computer simulation technology. For concert halls such as the Kauffman Center project that have unique architectural configurations, the scale model is a powerful tool of the acoustical consultant during the design phase of the project. This tool is powerful because, by generating sound in the scale model and measuring how it interacts with the hall's design, we can hear how the concert hall would sound if built to design specifications matching those of the scale model.

Our February, 2007 newsletter, carried an article that outlined the benefits of scale model testing in general, and I would like to underscore one of the points made in that article that is particularly relevant to the Kauffman Center project. As mentioned in that article, "we test for undesirable echoes, find their root causes and test echo mitigation remedies, and we measure the impulse responses and compare the physical data derived from those responses with data from existing halls."

To maximize the value of testing in the Kaufmann Center Concert Hall scale model, we checked the acoustics in every section of the hall, including multiple locations in the audience and stage areas. To do this, we set up sound measuring devices in a total of 38 locations in the scale model.

In the first round of testing, we began by looking for echoes, the most likely sound problem. After identifying the location of an echo, we judge the distance to the originating location from the response waveform. Using this distance as a guide, we determine the expected root cause of the echo, apply sound absorbing material to that location and conduct a retest to learn if the echo no longer occurs. This iterative testing requires steady perseverance. Because it is a sure way to identify the locations in a hall that would cause echoes and enables us to suppress these unwanted phenomena, it is a very important process.

With the results of our scale model testing in hand, we met with the Kauffman Center Concert Hall's architectural team to discuss the various options at each location identified as causing an echo. Depending on the location, the solution options included strategic placement of sound absorbing material, using or altering planned sound diffusing elements and adjusting the angle of certain wall surfaces. Thereafter, we updated the 1/10 scale model to reflect the design decisions and entered the second round of testing, which began with using our measuring devices to confirm that the echoes had been eliminated. When our testing passed this milestone, we proceeded to the final validation of obtaining impulse response data from the scale model, calculating the acoustical properties that can be derived from the data and analyzing the data in comparison to data for existing concert halls. At the end of these efforts, we successfully concluded the scale model testing.

In these few paragraphs, I hope to have provided the reader with an overview of the process we used to perform scale model testing for the Concert Hall at the Kauffman Center for the Performing Arts site in Kansas City, Missouri. Our testing resulted in modifications that have been incorporated into the project's design. Currently, the project is in the midst of the construction phase.

Retrospective on Ueno Gakuen University's Ishibashi Memorial Hall

by Dr. Minoru Nagata, Founder of Nagata Acoustics

<< Why Write about Ishibashi Hall Now? >>

Ishibashi Memorial Hall was constructed in the Higashi Ueno section of Tokyo's Taito Ward to commemorate the 70th anniversary of the founding of the then all-girls music conservatory Ueno Gakuen (now a middle school, high school and university of the same name). Nissoken Company served as the project architect and construction manager and Obayashi Gumi Corporation built the hall. Ishibashi Memorial Hall opened in November 1974.

Today, Tokyo has more than 15 large and small concert halls operating with nearly full daily schedules. These halls and their programming have eclipsed the presence of Ishibashi Memorial Hall. But this hall, with its 36-stop pipe organ at the front of the auditorium and seating for an audience of 600, deserves to be remembered for the significant role it has played in the performing arts life of the city. Not so long ago, performers and classical music lovers avidly selected this hall for their recitals, chamber music ensemble concerts and choral performances.

Ueno Gakuen University's history now dates back more than 100 years. The school has maintained many traditions and has also set out on new paths in response to the needs of new generations. Examples of recent changes made by the school are a co-ed admission policy that accepts young men as well as young women and the building of a new Ueno Gakuen campus that brought the middle school, high school and university under one high-rise roof, a project in which Nagata Acoustics participated.

Another change underway is the reconstruction of the 33-year old Ishibashi Memorial Concert Hall at its original location. Currently, demolition work is in progress and by next March, the original Ishibashi Memorial Concert Hall will be totally gone. Then, in the spring of 2010, a new hall with a new architecture and acoustical design will rise and stand in its place.

My connection with Ishibashi Memorial hall began in 1972, about a year after I founded Nagata Acoustics. It was my first concert hall project.

The era was 25 years after the end of World War II, and young, musically talented Japanese people dreamed of having a stage where they could perform classical music. The ambitious and courageous decision of the then head of Ueno Gakuen, the late Dr. Masue Ishibashi, together with the efforts of the architect and other project team members gave birth to this hall and its 33-year career as a performance venue. In their memory and honor, I will share the story of the making of Ishibashi Memorial Hall and some comments about what made this hall special.

<< The Japanese Acoustical Design Milieu of the Early 1970s >>

In the early 1970s, when Ishibashi Memorial Hall was conceived, Japan was busy building prefectural and civic auditoriums throughout the country. I was kept very busy designing these kinds of facilities. From the acoustical design perspective, however, the designs of the prefectural halls and civic halls all followed the design methodology and technology that we pioneered for the Tokyo Bunka Kaikan project.

A few years earlier, in 1963, I had benefited from the opportunity to spend a year studying in Germany. I attended Goettingen University, where I participated in research on lateral sound reflections, and I also experienced the sound of classical music concerts in both the Vienna Musikverein and the Berlin Philharmonic Hall, which had just opened. Both the acoustics of Vienna's shoebox configuration and of Berlin's vineyard configuration offered the audience sound experiences unlike the sound of Japan's multipurpose halls.

I desired to create the acoustics of a concert hall at home in Japan, but as long as the goal of every Japanese hall project was multipurpose acoustics, this desire remained unfulfilled. So my first opportunity to develop a hall design using lateral sound reflections became the Ishibashi Memorial Hall project.

<< Designing Ishibashi Memorial Hall >>

I was brought onto the Ishibashi Memorial Hall project at the end of the project's design phase. The site of the project created constraints on the hall's size and shape, and decisions had already been made that the hall would be one floor only (no balconies), have a nearly rectangular footprint and have a ceiling that sloped downward from the stage toward the rear of the audience seating area.

Given this starting point, I set forth the following specifications:

  • In order to provide the appropriate acoustical environment for the lower registers of the pipe organ, use concrete for the sidewalls of the auditorium and construct the ceiling of a heavy material.
  • In order to promote sound reflections from the sidewalls, make a portion of the accordion-pleated wall surfaces of the sidewalls parallel to the center axis of the hall.

The plan and cross-section views of the completed Ishibashi Memorial Hall can be seen in the accompanying drawings. The plan view of the hall shows the hall's adjacent relationship to the building's Aeolian Hall, which seats 120. Over the years, Aeolian Hall has been used especially for the performance of ancient and baroque music genres.

Fig-1 Plan View of Ishibashi Memorial Hall
Fig-1 Plan View of Ishibashi Memorial Hall
Fig-2 Cross-section View of Ishibashi Memorial Hall
Fig-2 Cross-section View of Ishibashi Memorial Hall

At the request of the late school headmaster, Dr. Ishibashi, Ishibashi Memorial Hall also included annual performances of Ishibashi Noh. The inclusion of Noh and Kyogen among the hall's program offerings was certainly one of the unusual and endearing traditions of this classical music concert hall. When the reconstructed hall opens in 2010, the tradition of annual Noh performances will be continued.

Fig-3 Reverberation Time of Ishibashi Memorial Hall
Fig-3 Reverberation Time of Ishibashi Memorial Hall

Ishibashi Memorial Hall's measured reverberation time is shown in the accompanying graph. As the graph clearly shows, the hall's reverberation time tends to increase within the low frequency ranges and also within the high to middle frequency ranges. This reverberation characteristic is truly the unique aspect of Ishibashi Memorial Hall's acoustics. The dip in reverberation time exhibited in the 250 - 500 Hz band is likely due to the vibration from the two layers of 12 mm (.47") calcium silicate board used on the hall's ceiling.

<< Early and Ongoing Reviews of Ishibashi Memorial Hall >>

When Ishibashi Memorial Hall opened, the hall's acoustics immediately made a strong impression on audiences, and critiques of the hall included those that expressed praise and those that expressed dismay. In particular, some of Ueno Gakuen's piano instructors continued to find fault with the hall's acoustics for quite some time after the hall's opening. In an era when there were no concert halls in Tokyo with rich acoustics, it is no surprise that the new 600-seat hall with 1.5 second reverberation time bewildered some performers. Nowadays, with the plethora of halls with rich acoustics in many parts of Japan, Ishibashi Memorial Hall's acoustics seem to me to be a good example of the "golden mean" of reverberation time appropriate to a small hall. Pianist Sachio Yokoyama, currently a professor of piano at Ueno Gakuen University, praises Ishibashi Memorial Hall's acoustics highly.

<< The Close of a Hall and the Close of an Era >>

After Ishibashi Memorial Hall opened and another 10 years or so passed, Japan's cultural landscape experienced the concert hall building boom of the 1980s. In central Tokyo alone, the number of small concert hall venues exceeds 10 halls, and each one offers programming that matches the specific acoustical characteristics that distinguish it from other halls.

In the midst of the great tide of classical concert activity in Tokyo, I find it truly regrettable that Ishibashi Memorial Hall's existence has come to be overshadowed. When the reconstructed hall opens its doors a few years hence, I hope that the new Ishibashi Memorial Hall will become a desired and well-attended venue.

Nagata Acoustics Inc.
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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E-mail: info@nagata.co.jp

[ Japanese Version ]