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

Nagata Acoustics News 98-11iNo.131j
Issued : November 25, 1998

Houfu Regional Community Center--"Aspirat Hall" Opens

by Satoru Ikeda

Houfu Regional Community Center--"Aspirat Hall"
In Houfu City, Yamaguchi Prefecture, a new regional community center named "Aspirat Hall" opened its doors on October 30, 1998. The new community center is located at the center of the city on a site directly in front of the north exit of the Houfu City JR train station. Houfu City is well known in Japan for its famous Houfu Tenmangu Shrine, as well as for the historical Mori Manor and as the birthplace of Santoka Inada, a 20th century haiku poet thought by some to rival Basho, the internationally known 17th century haiku master.

Acknowledging Houfu City's rich cultural heritage, the goal of the planners of Aspirat Hall is that by bringing together much of the local cultural and other social activity, the people of Houfu City will stimulate renewal in the city's central area. In addition, the planners hope that in the process of using the new facility, the very purposes for which community members come to Aspirat Hall and the surrounding neighborhood will also grow and expand as well. As is true of the neighborhoods around central train stations in many mid-sized and small Japanese cities far from the major metropolitan areas, shoppers and businesses have increasingly disappeared from the traditional shopping and commercial neighborhood near Houfu City JR Station. Aspirat Hall's planners hope that the community center will turn the trend around and revitalize both the commercial as well as the cultural vitality of the inner city. Like numerous other community and cultural centers built by Japan's regional cities, Aspirat Hall opened its doors saddled with a heavy load of expectations from those who supported and planned it.

<< Summary of the Facility >>

Aspirat Hall's architectural design draws its inspiration from the hall's lofty objectives of stimulating community involvement and informational and cultural exchange. A main feature of the structure is a glass curtain wall that thrusts up 16m high to the ceiling of the building, creating an airy, expansive public space for people to gather. Also on the first (ground) level are a Houfu Information Corner, a room displaying a permanent exhibition about Santoka Inada, and a pavilion named for the writer Nosho Omura. The second floor has an exhibition hall and rehearsal and practice rooms, and Aspirat Hall's concert hall is located on the third floor. Of particular architectural note are the design of the passageway from the public space to the hall, which was inspired by the approach at Houfu Tenmangu Shrine, and the design of the upper portion of the concert hall, which was has a motif inspired by the ancient log cabin architecture of the region. These aspects of the design tie the structure to Houfu's history, recreating the old in new form. Nihon Sekkei was responsible for the architectural design and project management. The main contractor was Kajima Corporation, working together with a consortium of other companies.

<< The Concert Hall's Size and Configuration >>

Prior to the construction of Aspirat Hall, Houfu City's main performance venue was Houfu Kokaido, built in 1960, and seating an audience of 1800 persons. As was true of an earlier project of ours in Hakodate, Hokkaido (see the 1998.5 News), some of the original supporters of a new hall in Houfu thought that they wanted another medium-sized hall similar to the existing Kokaido. In the end, however, the decision was made for the Aspirat Hall concert hall to seat an audience of approximately 600 persons.

Once the decision was made for the hall to be a concert hall of 600-seat capacity, this information and the characteristics of the site led us to propose that the hall have a shoebox configuration, this configuration being well-known for its excellent acoustical reputation. We then considered the configuration of the hall's side balcony and decided that the concert hall would have a single balcony in a space 17m wide x 31m deep x 15m high.

The next step in our planning was the determination of a finished interior that would enable sound diffusion in the hall and the selection of materials that would not radically impact the space from a sound absorption perspective. In addition, to the extent that we could do so unobtrusively, our design also included innovative means that enable limited adjustment of the hall's reverberation time for speaking engagements and other non-classical music concert use. The adjustable reverberation time is achieved in part through the design of the stage, which can be temporarily customized to respond to the needs of different instruments and ensembles, and the preferences of different conductors and performers.

Concert Hall
<< Unique Aspects of the Concert Hall >>

Unlike a typical shoebox hall, when one looks up at the ceiling of Aspirat Hall's concert hall, one sees a strikingly unique design. The ceiling is mainly of uneven ribbed construction that looks like an undulating river. At the sides, the ceiling folds downward and becomes glass paneling that, beside the river-like ceiling, looks like brooks flowing on each side. The hall's side walls are also noticeably ribbed above and below the balcony level.

On the orchestra-level, the side walls are of multi-layered construction. The walls were irregularly shaped to make the reflected sound being diffused and the acoustically transparent ribbing structure was covered over the shaped walls. In between these two structures, the shaped walls and the ribbing surfaces, we installed an electrically movable curtain that can be used to adjust the hall's reverberation.

The other adjustable apparatus of the hall is installed at the sides of the stage and enables minor changes in the stage's reverberation characteristics. Here, we used movable wings that affect the surface reflections and rear sound absorption specifications.

With the adjustable stage wings closed and the reverberation-dampening curtains not in use, i.e. when the hall is adjusted for its longest reverberation time, the reverberation measurement is 2.1 seconds (empty hall) and 1.8 seconds (full audience). When the movable stage wings are set out to increase the sound absorption, and the side wall curtains are deployed, i.e. when the hall is adjusted to absorb as much sound as possible, the reverberation time is 1.6 seconds (empty hall) and 1.4 seconds (full audience). These measurements are at 500 Hz and include a 0.4 second margin of variance. I also tested and confirmed that when the hall is adjusted between its longest and shortest reverberation settings, the difference is well distinguishable to the average human ear.

<< Concert Hall Sound Isolation and Sound System >>

Two aspects of the concert hall's acoustical engineering that required special attention were sound isolation from external noise and the selection of a main speaker and its housing as part of our planning for the sound system. We faced a double challenge with regard to sound isolation. Of first concern was isolation from the railway line in near proximity. The line that runs directly in front of the community center is the Sanyo Line, a trunk line with heavy use by not only passenger trains, but freight transport as well. We needed a strategy to isolate and decrease the noise and vibrations from this source. In addition, the architectural layout of the community center stacks the rehearsal and practice rooms and exhibition hall underneath the concert hall, a layout that does not make sound isolation easy.

Given the challenges we faced, I chose a floating structure for the concert hall and the rehearsal and practice rooms. (Our planning assumes frequent loud sound volumes for the rehearsal and practice rooms.) Consequently, sound and vibration from the railway line has been sufficiently shut out of the concert hall and related rooms, so that it is not heard at all.

In the concert hall, we faced the often encountered dilemma of wanting both to install a sound system that would produce maximum clarity and to preserve the architect's intention in designing the ambiance of a classical music hall. For Aspirat Hall's concert hall, we happily agreed on oval-shaped main speakers that hang visibly suspended above the stage lights. The result shows a natural functionality and is unobtrusive. I sincerely want to thank the architect for the understanding attitude demonstrated as we worked through this part of the design process.

<< Compliments from the Inaugural Conductor >>

The concert hall's inaugural concert performers were the Deutsche Bach Solisten under the baton of Maestro Helmut Winschermann. The Aspirat Hall performance was the first stop on their Japan Tour and this undoubtedly contributed to the length of the ensemble's rehearsal on the day immediately preceding opening night. In our estimation, it was really a long rehearsal! During the opening event, we had the opportunity to meet Maestro Winschermann, who kindly complimented us on the hall's acoustics and told us how pleased he was with the hall. At the opening concert, Aspirat Hall's General Manager addressed the inaugural concert's audience from the stage with Maestro Winschermann at his side. With deep emotion showing, the hall's General Manager shared with the audience the Maestro's delighted impressions of the new hall.

Maestro Winshermann's congratulatory words made for a relaxed and joyful mood from the outset of this concert. The ensemble and program were perfectly suited to the scale of the new concert hall. The evening was a grand success, with the lively and clear Bach interpretation enjoyed by all.

The Bach Solisten concert was wonderful, and if Aspirat Hall was located in Tokyo, it might well be planning similar world class programs on a regular basis. But in today's world situation, it is unlikely that a small regional venue like Aspirat Hall will be able to host such world-class ensembles on a regular basis. For the immediate future, three consecutive days of concerts by local ensembles are scheduled, as well as an amateur string ensemble class, cembalo instruction, and a local music festival.

Many concert halls dedicated to classical music have now been built or are planned in small and medium-sized locales throughout Japan, but the Aspirat Hall concert hall is the first on a scale of 600 seats in Yamaguchi Prefecture. Naturally, there are some limitations as to the kind of performances that will be appropriate to the new hall. However, by building on the prefecture's experience in the successful operation of its much larger Kokaido, the new hall should provide a complementary alternative and many opportunities to create true sharing of creativity through a kind of two theater complex approach to event and performance planning. We look forward to hearing rave reviews about the performances and other events and activities at Aspirat Hall's new concert hall.

More information about Houfu Regional Community Center can be obtained by writing to the center at 1-1-28, Ebisu-cho, Houfu City, Yamaguchi Prefecture; or by calling the center at 81-835-26-5151.)

Sound System for Concert Halls -- Part 1 in a Series

by Katsuji Naniwa

In Japan, the development of electrical acoustic sound system for performance venues has proceeded hand-in-hand with the proliferation of multipurpose hall construction. The technology and understanding of design strategies for sound system equipment in multipurpose halls already boasts a long history in Japan, where there are many examples of sound system equipment implementation and operation in multipurpose halls. There are also many professionals involved with the sound system at these venues.

In the past ten years, however, Japan has seen a rapid trend toward construction of concert halls designed especially for the performance of classical music, and I have been responsible for the sound system design of many of these concert halls. Now, as I consider the state of technical design strategies and data collection for the sound system appropriate for these specialty halls, I am struck by the lack of any accumulated body of work or consensus in the field. The development of sound system design strategies and data for use in designing the sound system of classical music concert halls has simply not kept pace with the marked growth of this kind of hall.

That the design technologies and principles applied to multipurpose halls cannot simply be adopted as is when designing the sound system of a concert hall is only one of the dilemmas that I have encountered. Another stumbling block is the lack of understanding of the role of sound system on the part of some individuals in the classical music industry. Judging from the considerably large number of people who still question why a hall needs speakers at all if it is intended to be used only for live performances, the pervasive ignorance about the role of sound system is clear to me, and a problem that I would like to help remedy. Accordingly, in the next several months, I will introduce some current thinking and design strategies as well as observations from projects on which the sound system design was my responsibility.

<< Distinguishing Aspects of Concert Hall Sound System >>

The most significant difference between concert hall sound system and the sound system for multipurpose halls lies in the principle that concert halls do not electrically amplify the music produced on stage by the performer(s). Other differences include whether or not the hall installs equipment for amplification of the spoken word, equipment designed specifically for the recording of classical music, hall staff intra-communication equipment, and hall monitoring equipment.

<< Wooing Non-classical Performances to Classical Music Concert Halls >>

The need for equipment to amplify the kinds of music generally performed in concert halls is at most minimal. When concert hall performances do require amplification, typically it is to enhance the volume of a particularly weak instrument or group of instruments, or in connection with the performance of computer music. In either of these situations, amplification is limited to a portion of the instruments that perform on the concert hall stage.

However, because the administrators of most concert halls are eager to expand the use of their halls, they strongly desire to woo bookings of non-classical events and performances that would otherwise take place in multipurpose facilities. Consequently, more and more classical music concert halls are considering installing sound system that is clearly intended to support non-classical music performances and events. Therefore. the increasingly complex and diversified operational plans of today's concert halls is yet another factor that should be kept in mind in the design of the sound system for each concert hall project.

<< Specific Issues in Designing Concert Hall Sound System >>

The following issues are among the necessary considerations in designing sound system for a concert hall:

* Achieving clarity of amplified speech.
* Determining the speaker system's configuration, placement, and installation, as well as ensuring conformity with the acoustical characteristics of the hall.
* Devising strategies to enable the hall to be used for other purposes than as a concert hall.
* Evaluating the hall's approach to recording performances and its recording equipment needs.

<< Achieving Clarity of Amplified Speech >>

In concert halls, speech amplification equipment enables both hall-wide public announcements and lecture concerts, as well as other spoken communication between the audience and the hall administration and/or performers on stage. The clarity of amplified speech is therefore an essential and important function of the sound system of any concert hall, and a very worthy topic of focus for my first article here on concert hall sound system.

Compared with multipurpose halls, the acoustical designs of concert halls feature longer reverberation times. However, the rich sound of longer reverberation times is the acoustical arch enemy of clear speech. The reverberations form a kind of mask over the sound of the spoken words and make them difficult for the ear to comprehend. The best strategy for eliminating this problem is to broadcast the amplified speech only in the audience seating area and impede the sound generated by the speakers from going to any other parts of the hall. Unfortunately, it is impossible to accomplish this completely because it is impossible to totally control the directions that the sound emitted by speakers will travel. Specifically, the lower the register of sound, the longer is the sound wave, taking it outside the bounds of control of the size of speakers currently in use.

The sound frequency of human speech is in the range of 250 Hz; and the length of this frequency of sound wave is 1.36m. Based on theories of acoustical technology, we know that the size of the audio speaker would have to be larger than 1.36m in depth in order to be able to apply directional characteristics to it for the sound waves produced by human speech. Because such a large speaker is impossible in a concert hall environment, smaller speakers are used and the critical low and middle register sounds of human speech travel not only directly to the audience's ears but also to the walls and ceiling of the hall, increasing the reverberation sounds and negatively affecting the clarity of the amplification.

<< Partial Remedies to Improve the Clarity of Amplified Speech >>

To some extent, the lack of clarity can be ameliorated through the use of sound system equipment. One method is to eliminate the speech's lower registers using a tone controller. This fix certainly decreases the reverberation sound and thereby its negative affect on the clarity of the amplified speech. Unfortunately, the downside is that this technique employs the tone controller to control reverberation time--not its intended purpose. In so doing, it emaciates the tone of the amplified speech, giving it an unsavory and dried-out tone.

Another equipment-based fix is to install audio speakers fitted with woofers for the low registers. The downside of this remedy is the large size of such speakers, which invariably look out of place in concert halls.

In addition to the challenges discussed above, when we gauge the coverage area of individual speaker systems, we generally use the sound equalizer information provided by the speaker system's manufacturer. In multipurpose halls, the comparatively short reverberation times mean that, with regard to the equalization level at the front of the speakers, a wide coverage area of up to -6 dB can be utilized. However, in concert halls, the long reverberation times overpower the speakers and limit an equalizer's coverage area to a narrow -3 dB. The result is that more speakers are needed in the concert hall to achieve the same intensity of amplified sound.

<< The Importance of Both Clarity and Natural Sounding Speech >>

When clarity of speech is compromised and the spoken word is difficult for an audience to comprehend, the resulting complaints come fast and, ironically, have their own precise clarity. Clearly heard speech is fundamental to acoustical planning, but from the professional's perspective, natural sounding speech tones are also a critical and essential standard to be achieved. Everyone is an expert at hearing human speech, and an audience is just as quick to notice the quality of amplified human speech as it is to judge its clarity. From a technical standpoint, it is even more challenging to ensure that amplified speech will have a natural sounding quality than it is to achieve clarity, since naturalness is a characteristic that is difficult to quantify, and is the result of a combination of factors that elude prediction during the acoustical design phase of a project. Together with our work on achieving clarity, therefore, our current strategy must be to continue to gather data and make evaluations based on actual listening observations. It is through these efforts and ongoing critical and innovative thinking that further improvements will be realized in speech amplification in concert halls.

Report on the 136th Meeting of the Acoustical Society of America's Architectural Acoustics Session: "Acoustics of Halls with Organs"

by Dr. Minoru Nagata

The Acoustical Society of America held its 136th meeting for during the five-day period October 12 through 16, 1998, in Norfolk, Virginia. On October 16, one of the full-day sessions (8:00 a.m. - 6:30 p.m.) was "Acoustics of Halls with Organs." The session included 16 invited presentations and 2 general presentations, and concluded with an open participation forum. The entire day's session was chaired by Dan Clayton.

The "Acoustics of Halls with Organs" session began with Mr. Clayton presenting a 20-minute overview of the development of the organ from its first appearance in the third century through the instrument's history during the 20th century. Thereafter, during the course of the entire day's presentations, I came to understand that, in the United States, many universities and colleges have organs installed in their halls. The content of the majority of the session's presentations focused on introducing the audience to specific examples of halls that have organs.

Among the many presentations, one that I found most notable and filled with erudition was on Sweden's Goteborg Organ Art Center. In the report on the center's venerable 16th century organ, the presenter's research spanned an analysis of the composition of the organ's pipes that elucidated the secret of the instrument's tone color, an explanation of the organ's mechanisms, and a discussion of the way the instrument is played. I enjoyed the thoroughness of this presentation and the completeness of the presenter's research.

In my own presentation, I made four main points. First, I discussed my observation that in all designs of halls with organs one of the following four principles is implemented: (1) Priority is given to the organ. (2) Priority is given to an orchestra. (3) The importance of the organ and the orchestra are considered to be on equal footing. (4) No special consideration is given to the organ at all. Secondly, I introduced the Tokyo Metropolitan Art Space Garnier organ and the Casals Hall Ahrend organ as distinctive examples of recently constructed concert organs. Third, I discussed influences on the acoustical characteristics of the two organs and the response of music fans in the Casals Hall. Fourth and lastly, I compared the viewpoints of organ builders, as represented by Mr. Ahrend, builder of the Casals Hall organ, and the organ builders of the Fisk organ installed in Yokohama Minato Mirai Hall with regard to concert hall acoustics.

Nagata Acoustics News 98-11iNo.131j
Issued : November 25, 1998

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