Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 12-02 (No.290)

Issued : February 25, 2012

[ Japanese Version ]

Kansas City's New Concert Hall - The First Subscription Concerts of Its Inaugural Season

By Motoo Komoda

Kansas City Symphony Orchestra
Kansas City Symphony Orchestra

As we reported in the December, 2011 issue of this newsletter, the gala opening of Kansas City's new performing arts center included the first subscription concerts in the center's 1,600-seat concert hall (named Helzberg Hall). On September 23 - 25, Kansas City Symphony Orchestra performed these first subscription concerts under the direction of Maestro Michael Stern, the orchestra's musical director and principal conductor.

<< Inaugural Subscription Concerts' Program >>

The orchestra selected a fine choice of works for the hall's opening performances:

  • Stravinsky's "Fireworks"
  • Beethoven's Piano Concert No. 5 "Emperor" with guest artist Emanuel Ax
  • Chen Yi's "Fountains of Kansas" (world premiere)
  • Respighi's "The Pines of Rome"

The orchestra performed the program in the same order on all three evenings, starting with the short Stravinsky piece and continuing immediately with the "Emperor" concerto featuring the hugely popular pianist Emanuel Ax. Then came the intermission followed by the commissioned world premiere. A wonderfully colorful orchestration of "The Pines of Rome" concluded the evenings. The program's diverse musical content offered subscription patrons an appropriately eclectic sampling of compositions and sound for their first experience in the new hall.

<< Helzberg Hall's Elliptical Shape and Room Acoustical Design >>

Plan view of Helzberg Hall
Plan view of Helzberg Hall

Section view of Helzberg Hall
Section view of Helzberg Hall

A defining aspect of Nagata Acoustics' design of Helzberg Hall is our use of blocks of audience seating surrounding the orchestra's stage in a vineyard configuration. We strategically positioned the height of each block of seats independently of the other blocks so that partial wall surfaces between the blocks serve as effective sound reflecting surfaces. We strategically determined the angles and other properties of these surfaces to maximize the surfaces' acoustical effectiveness.

Overall, the hall interior has a nearly elliptical shape. Using an elliptical shape for a hall's basic footprint creates a very difficult starting point for acoustical room design. In the case of Helzberg Hall, we installed acoustically transparent slats on the long walls that run alongside the blocks of audience seating and behind the slats we placed convex or stepped protrusions to prevent undesirable sound focusing while retaining the appearance of walls with smooth lines.

The slats installed on both side walls of the audience seating area are constructed of a combination of wood slat sections and plastic netting. Behind the slats we arranged the protrusions continuously along the walls. We also employed a similar treatment at the eye-catching rear wall of the stage, which is draped in fine metal slats that bear some visual affinity to the performing arts center's exterior. The material of the metal slats is so fine that some call it a mesh. This rear wall forms a very large concave surface and we placed stepped protrusions behind the metal slats (except for the center portion of the wall where the pipe organ is installed).

We used the 1/10 scale model discussed in our newsletter's December, 2007 issue as well as full-size models of the protrusions to carefully and iteratively test, confirm and reassess portions of the hall's design. As a result, in the completed Helzberg Hall the acoustics are free of echoes and undesirable sound focusing phenomena.

Reverberation time of Helzberg Hall
Reverberation time of Helzberg Hall

At midrange frequency (500 Hz), we measured a reverberation time of 2.3 seconds in the empty Helzberg Hall. The calculated reverberation time for the full hall is 2.1 seconds. We intentionally achieved a relatively long reverberation time for low frequencies to give an overall sense of warmth to the acoustics.

<< Attending the Inaugural Subscription Concerts and Highlights of "The Pines of Rome" Performance >>

I had the pleasure of listening to the superb performances of all three nights of the inaugural subscription concerts. On one evening, I sat in the middle of the Parterre section of the main floor, on another night in the Lower Grand Tier and on the third night in one of the side mezzanine seats. Beyond the enjoyment of the totally satisfying performances, I also derived huge delight from the rare opportunity to experience, on consecutive nights, three views of the stage from three different angles and the intimacy of being enveloped in and among three full-house audiences of subscription patrons.

Performances of Respighi's "The Pines of Rome" typically locate the composition's "banda" musicians away from the orchestra on stage. For Helzberg Hall's inaugural concerts, the trumpet and the trombone were separated, with one playing from the right Lower Grand Terrace and one from the left Lower Grand Terrace, while the French horn was creatively placed above the stage rear at the organ player's seat. This staging added special visual appeal to the performance.

Another especially well-produced moment of Respighi's "The Pines of Rome" was the nightingale's voice which was reproduced from a loudspeaker set behind the wood slats at the stage rear. When the first notes of the nightingale's call began, the originating location of the nightingale's voice was not obvious, increasing the illusion of a real nightingale singing somewhere and enhancing the effect of this unique part of the composition. This work and the concerts' entire program showcased to good advantage the new hall's acoustical characteristics.

After the great success of the inaugural concerts, the hall's calendar continues to be booked with performance after performance. I hope that the spectacular interior of the hall and its beautiful acoustics will be enjoyed by music patrons for many years to come.

The Kauffman Center for the Performing Arts home page can be found at http://www.kauffmancenter.org/.

New "Makabe Densho-kan" Preserves the Historical Look of Its Town

By Chiaki Ishiwata

Makabe Hall cross sectional view
Makabe Hall cross sectional view

In the Makabe-cho district of Sakuragawa City, Ibaraki Prefecture, a new multipurpose facility opened in autumn, 2011. The facility, named Makabe Densho-kan ("densho" means "to hand down traditions" and "kan" is a suffix denoting a building) combines a hall, library, museum, meeting rooms and traditional Japanese tatami rooms. The town of Makabe-cho became incorporated into Sakuragawa City in 2005.

<< A Town Steeped in History and Appropriate Architecture for the Historical District >>

Makabe-cho is located north of Mt. Tsukuba in central Ibaraki Prefecture. The town's formation dates back to the days when there was a Makabe Castle and the town grew into existence in its shadow. The town's long history and the former castle have received national Japanese recognition through the castle location's designation as a Japanese national historic site. Also, Makabe-cho has numerous examples of traditional Japanese architecture built during the Edo Period (1603 -1868) and thereafter, earning the district distinction as a designated national architectural historic preservation district.

Makabe Densho-kan was built within the boundaries of the historic preservation district. The new building's architect, ADH Architects, was selected via a proposal process in which ADH Architects' proposed design approach emphasized creating a design appropriate to the historic preservation district location. From the proposal stage of the project, ADH Architects used the technique of obtaining data "sampling" of special characteristics and proportions used in 26 of the district's historic buildings. The architect then assembled these elements into a new design to fit the specific site and Makabe Densho-kan's functional needs, creating and proposing a new architectural scenery. The resulting exterior of Makabe Densho-kan has both unique architectural aspects and a look that blends exceptionally well with the historical architecture of the neighborhood.

<< Acoustical Design of Makabe Densho-kan >>

Makabe Hall interior
Makabe Hall interior

Makabe Hall side wall
Makabe Hall side wall

Nagata Acoustics served as the acoustical consultant for the Makabe Densho-kan project. The hall holds 300 seats of tiered audience seating and can also be configured without the seating as a flat-floored room for indoor athletic recreation. When configured with the audience tiered seating, the hall will be used as an auditorium for ceremonies, lectures, recitals and similar events.

When I first reviewed the Makabe Densho-kan's design drawings, I thought the gabled roof outline to be a unique and new design. That was before I had ever visited Makabe-cho. When I visited Makabe-cho and the project site, I saw a number of roofs with the same angle as that of Makabe Densho-kan's gabled roof. I recognized the roof line in the historic buildings and gained full appreciation for why this particular design is used for the Makabe Densho-kan roof.

For the acoustical design of the hall's interior, I began by considering how the acoustics would be affected by translating the gabled roof angles to the interior ceiling of the hall. In the flat-floor configuration of the hall, the angles play a beneficial role in preventing undesirable sound phenomena that might otherwise occur when sound bounces back and forth between the floor and the ceiling.

Because the hall will be used for indoor athletics in its flat-floor configuration, and people using the hall might bump against the side walls while participating in activities, I specified smooth surfaces for the lower portions of the hall's side walls. To balance the use of smooth wall treatments, I specified sections of sound absorbing-materials in an alternating pattern on the right and left side walls. I gave the upper portions of the walls an uneven finish that promotes sound diffusion.

On both the ceiling and the walls, I used perforated plywood backed by glass wool as the sound-absorbing finish material and for the hall's day-to-day activities achieved an easy-to-use, shortish reverberation time for the room. I used a perforated finish material throughout the hall, backing it with either a solid layer of sound-reflecting material to create a sound-reflecting surface or with glass wool where sound-absorbing surfaces are needed. In this way, I created a consistent visual appearance for both sound-reflecting and sound-absorbing surfaces.

<< Visiting Makabe-cho and "Hinamatsuri" >>

This article will appear on the Web shortly before Japan's annual "Hinamatsuri". (The Japanese Doll Festival for girls is held every year on March 3.) While I have not had the pleasure of being in Makabe-cho during the festival period, I know that the town has a reputation for impressive "Hina" doll displays, so this is an excellent time of year to visit Makabe-cho's historical district and enjoy Hinamatsuri as well.

For photos and more information about the March 3 Hinamatsuri (Japanese doll festival) and about Sakuragawa City, see http://www.city.sakuragawa.lg.jp/index.php?code=1588.

For a video tour of Makabe Densho-kan, see http://www.youtube.com/watch?v=VtV6aWmPlFM.

My Retrospective on Building 1/10 Acoustical Scale Models - Part 2:

"The power of the architect's voice . . ." (Hitachi Civic Center Concert Hall, 11/1988 - 3/1989)

By Nobuyuki Ebihara

"How long does it take to build the 1/10 scale model of a concert hall ?" I'm frequently asked this question and when I reply that it takes from four to six months, just about everyone who hears my answer expresses surprise. They ask, "Why does a 1/10 scale model take so long to build?" In fact, I've done projects that took even longer to complete.

To answer the question of why building a 1/10 scale model takes as long as it does, let me begin with an analogy. For example, if you compare a cardboard box to one die of a pair of dice, both will have the same eight pointy corners. Regardless of how large the size of the cardboard box is and how small the die, as long as they have the same shape, the shape determines that they both have the same number of pointy corners.

If the design of a concert hall has a surface with a thousand pointy protrusions, then the 1/10 scale model also needs to have exactly the same number of pointy protrusions. In the 1/10 scale model, the points will be closer together than in the hall, but other than this difference, there's no difference between the number and shape of the points in the 1/10 scale model and in the hall. In addition, before I build a concert hall's 1/10 scale model, the hall's typically complex design exists only in two-dimensional drawings, so when I transform the design into the three-dimensional 1/10 scale model, I become the first person to do the work of finding and figuring out what to do with the parts of the design that cannot be built as drawn because of realities in the three-dimensional physical world.

For these reasons, building a 1/10 scale model ends up taking quite a lot of time and these reasons also explain why it's difficult for me to estimate how fast the work will progress or when I'll be able to complete specific parts of the model. Promising to complete the 1/10 scale model by a specific date can be risky business.

<< Lessons Learned while Building the Hitachi Civic Center Concert Hall's 1/10 Scale Model >>

I built the Hitachi Civic Center Concert Hall's 1/10 Scale Model at Kajima Technical Research Institute, a facility of the project's general contractor. (The hall is located in Hitachi City, Ibaraki Prefecture. Kajima Technical Research Institute has several locations in Tokyo suburbs and nearby prefectures, and I built the model at one of these institute locations.) This concert hall has slightly more than 800 seats and a shoebox configuration. These two characteristics did not raise any red flags as I began my work and I made good progress constructing the 1/10 scale model's shell. I built the model on a rigid concrete base and when I measured the shell with a surveyor's transit, the baseline had no misalignments at all.

One day, after I'd completed the shell and begun work on the stepped first floor audience level and balcony tier, chief engineer Mr. Shin-ichiro Kan came by and said, "Three weeks from now the principal design architect will visit the institute. Would it be out of the question to attach the side wall diffusing elements to the scale model in time for him to see them when he visits?"

Without much thought I replied "I'll get it done."

However, soon thereafter I encountered this model's first time-consuming and difficult element. I needed to figure out what angles to use for the handrails along the left and right sides of the balcony. Next, calculating the dimensions of the side walls' diffusing elements became a difficult puzzle to solve. Even though I might be using the simple medium of 9 mm. (0.35 in.) plywood to create the protruding shapes indicated in the architectural design, at each step of the work I needed to ask questions about the proper angles of the various faces of the protrusions. Otherwise, I would not be able to obtain a beautiful fit when I assembled the surfaces to form the protrusions.

At the time, I began the multi-step process I used in those days. First, I would make a full-size version of each of the diffusing elements. Then, to increase the precision of my work, I measured the shapes' dimensions and angles and calculated exactly how they would fit in the allotted space. This work consumed a huge amount of time.

the Hitachi Civic Center Concert Hall's 1/10 Scale Model: model-testing by Kajima Technical Research Institute
The Hitachi Civic Center Concert Hall's 1/10 Scale Model
model-testing by Kajima Technical Research Institute

The three weeks that followed my conversation with Mr. Kan vanished in an instant. I worked around the clock without sleep for the last 72 hours before the last day, but to no avail . . . and I ended up being on the receiving end of some very harshly worded criticism about missing the date. As shown in the photo, the diffusing elements around the walls above the stage were in a state of only partial completion when the principal design architect arrived.

Exhausted, I went to my car and was catching a few winks of sleep when Mr. Kan came to talk to me. He told me that the principal architect didn't like the way the peaks of the diffusing elements looked. The design had placed the peaks of the diffusing elements in a straight line and when the principal architect saw the design in three dimensions, he decided to change the design to a curved, wave-like placement. Mr. Kan continued, "Your incredible efforts of the past three weeks have come to naught. I am so sorry about this."

On concert hall projects, the hours of work expended by one carpenter building a scale model is a comparatively small amount of labor. I once heard an architect comment that "to create a better final product, we have to be willing to decisively get rid of some elements." In the incident I recounted here, the principal architect gave one change order and erased my three weeks of work.

<< Shin-ichiro Kan and How I Learned to Appreciate 1/10 Scale Models >>

Mr. Kan, who served as the senior engineer in charge of the acoustical testing, was a man well deserving of much praise. He was fair and respectful in all his interactions with the tradespeople. He never spoke condescendingly and, on the contrary, at the end of the workday he frequently invited me to join him for a bite to eat or a drink at a yakitori restaurant or a pub. On those occasions, our conversations mostly tended towards to non-work topics, but when I asked him a work-related question, he always obliged me by replying with clear and insight-filled answers.

Mr. Kan gave me my first understanding of the important role acoustical testing plays in the construction of a concert hall. He graciously taught me and explained many details. I'd always been passionate about accurately reproducing every detail of a project's design, but understanding what my work means to the overall project opened my eyes to a new perspective and, little by little, I changed some of the methods I use to build the scale models.

In the years since meeting Mr. Kan, my work on other scale models for acoustical testing has brought me into contact with lots of different people. I've discovered that, as was true of Mr. Kan, the more a V.I.P. deserves a place in society's top tier, the more likely he is to be free of prejudice towards tradespeople.

As for Mr. Kan, I continued to stay in touch with him for a few years after the project. Just when it seemed the time was ripe for this rising star to truly come into his own, he was suddenly taken from us. Even now, his loss saddens me. His research achievements established a path towards fine acoustics that I believe continues to be alive today.

Nagata Acoustics Inc.

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[ Japanese Version ]