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

Nagata Acoustics News 98-9iNo.129j
Issued : September 25, 1998

Nono's Prometeo and Akiyoshidai International Art Village

by Keiji Oguchi

Concert Hall (Prometeo arrangement)
The 10th Akiyoshidai International Contemporary Music Seminar and Festival was held from August 25 to August 31 at the new Akiyoshidai International Art Village in Yamaguchi Prefecture. The new Art Village was built in a valley located east of Akiyoshidai, which is famous for its karst geological formations. On the west side of the International Art Village, a mountain stands between it and Akiyoshidai. Indeed, the facility is surrounded on three sides by mountains, gracefully and naturally isolating it from the effects of man-made noise. Only the road that serves as the Art Village's approach opens onto flat land.

The new Art Village was conceived and executed with the aim of providing a venue for the Akiyoshidai International Contemporary Music Festival. The new facility is comprised of two buildings. One, that is shaped like a squared-off "U," contains a hall, lecture rooms and lesson studios. The other building contains dining and overnight accommodations. Yamaguchi Prefecture and the town of Akiyoshi sponsored the project. Arata Isozaki was responsible for the Art Village's architectural design.

<< History of the International Contemporary Music Seminar and Festival >>

The Akiyoshidai International Contemporary Music Seminar began in 1988 as the brainchild of Terumichi Tanaka, Associate Professor at Yamaguchi Junior Arts College, and Tatsuya Kawasoi, Associate Professor at Shimane University, in neighboring Shimane Prefecture. These two young contemporary music composers decided to establish a seminar to which they would invite a Japanese world famous composer, Toshio Hosokawa, as the artistic director of the Seminor & Festival.

Every summer, the Seminar and Festival invites a young composer or performing musician who is active in the genre of contemporary music. To date, the majority of invitees have been from Europe. The seminar part of the program is held during the daytime and concerts are performed in the evenings.

<< The Japan Premiere of Nono's Prometeo >>

This year, with the seminar and festival's 10th anniversary and the opening of Art Village coinciding in the same year, the Seminar and Festival planners put together an especially exciting program. Based on the suggestion of Toshio Hosokawa, the seminar and festival planners decided on Luigi Nono's opera, Prometeo, A tragedy for the ears, as the centerpiece event of the Art Village's opening festivities. This was the Japanese premiere of Prometeo, which was first performed in Venice in 1984, six years before the composer's death in 1990.

Prometeo is billed as an opera, but it is certainly not an opera in the conventional sense of that word. The work requires the placement of four orchestral ensembles and a chorus, plus instrumental and vocal soloists and narrators staged in two spiral formations that surround the audience like a crown on platforms set above it. In order to combine the sounds from these sources with "betrie" glass percussion instruments, add special effects, and provide amplification, 12 speakers must also be installed, at varying heights, inside each of the two spirals of performers. The audience, seated inside the spirals, hears the performance from multiple directions.

Abandoning the cohesiveness of a single conductor, the work must rely on two conductors because there is no vantage from which a single conductor can see all of the performers. At certain places in Prometeo, the two conductors proceed at different tempos.

While this phenomenon is influencing the performers, four electrical acoustic design and engineering professionals sit in the center of the performance area altering the output from the 12 speakers according to instructions included in Prometeo's score. The directions to these four "performers" include an array of digital acoustical effects such as filtering, delay, pitch shifts, reverberation lengthening (the longest of these lasting 30 seconds), amplification increases of equal durations, and the movement of sound images among the speakers. Occurring in real time, the playing of the live electronics part of the score is as critical to the performance as the interpretations of the scores of the more traditional performers, and the capabilities of the four acoustical electronics professionals are perhaps the most sensitive factor in ensuring that Prometeo is performed truly as the composer intended.

At Akiyoshidai, the chief among the digital acoustic professionals was Andre Richard. Mr. Richard is Director of South German Broadcasting's Heinrich-Strobel Stiftung Experimentalstudio, in Freiburg, Germany. Not only has Mr. Richard performed every staging of Prometeo since its world premiere, but I would venture to say that he is the only person who so completely comprehends Nono's intentions and can turn them into a performance reality.

<< The International Art Village Hall >>

Plan of main facility (2nd. floor)
The hall constructed at the Akiyoshidai International Art Village was designed expressly for the Prometeo performance. The hall's arrangement is most easily explained from the perspective of a person standing with his or her back to the large wall that, on its exterior faces the Art Village's courtyard. Chairless platforms are located directly in front of this wall, and on either side, directly before one and on either side. In addition, there are two tiers of stepped balconies with fixed seating. At ground level, the floor is flat, and the stage (on the courtyard side of the hall) is designed in forths, each of which can be raised or lowered independently.

For the performances of Prometeo, a temporary raised platform and the hall's chairless ground floor platforms were used to seat the performers. In addition to audience seating in the fixed balcony seats, additional audience space was provided on the ground level using stackable monroe chairs. Together, this enabled a total seating capacity for 450 persons. It should be noted that the backs of the balcony's fixed seating can be turned down (as with the podium seating of Kyoto Concert Hall) so that they can be used for additional seating of performers. This increases the flexibility of the placement and use of the stage area for future productions.

At the ceiling, the architect has designed projections that jut out from the ceiling. These are too large to be simply labeled diffusing elements.

According to Mr. Isozaki, he was inspired by the movement in Prometeo entitled "Islands," by the work Archipelago by author M. Cacciari, who also authored the text for Prometeo, and by the unique karst geography of Akiyoshidai.

<< Designing the Acoustics of the International Art Village Hall >>

When I was approached to provide acoustical consulting for Akiyoshidai International Art Village Hall, and learned of its unique architectural configuration, I realized that, for this project, I must jettison any assumptions based on the guiding principles generally employed in the acoustical design of concert halls. Usually, our work begins with selecting the hall's configuration, i.e., the fixed relationship between the hall's stage and the audience seating. However, for the hall of Akiyoshidai International Art Village, this relationship is not fixed! Even at this year's opening festival, the concerts other than Prometeo each set the stage in a different relationship to the audience.

So I began with two suggested priorities: (1) Ensure that the ceiling is high enough to engender a feeling of full-bodied sound; and, (2) Achieve a high standard of room quietness in anticipation of performance recording needs. Because the new hall would host performances of contemporary music, I suggested a rather short reverberation time of 1.2 seconds (at mid-range and with full occupancy). I based this suggestion on the assumption that clarity is an especially valuable acoustical characteristic for contemporary music. However, when I consulted with Mr. Richard, I learned that my assumption was off the mark. He advised me that the ideal reverberation time for Prometeo is approximately 1.8 seconds. Fortuitously, my suggestion for a high ceiling had been implemented with a ceiling that rises 12 meters from the hall's ground level. This architectural feature, combined with the stage and seating placement for the Prometeo production, enabled us to achieve a reverberation time of approximately 2 seconds (with the hall empty) for the Japan premiere.

<< A Focus on Quietness >>

In my approach to the hall's acoustics, I felt most strongly about the need for a high standard of quietness in this hall. My concern for this characteristic derived from the Akiyoshidai Seminar and Festival that I attended in 1996. During the performances at that festival, there were many moments when the works performed created an impact on the audiences through the adept use of silences meant to be "heard."

Assuring the hall's quietness was a race against time. The project's construction lasted until just days before the hall's scheduled opening, leaving no time for testing and fine-tuning. In particular, resolving the issue of the hall's ambient noise level dogged us to the very end, though we did finally succeed in reducing it to below NC-15 before the hall opened. But as fate would have it, on the night of Prometeo's Japan premiere performance, the audience did have to tolerate the uninvited "participation" of a flying insect that had somehow found its way into the hall.

<< Three Memorable Prometeo Japan Premiere Performances >>

In addition to the open rehearsal performance preceding opening night, I attended both of the performances of Prometeo at this year's Akiyoshidai International Contemporary Music Seminar and Festival. (It was performed on two consecutive evenings.) This major opus lasts more than two hours and is performed without intermission. The music itself lacks both tonality and melody. Nevertheless, and despite my lack of previous study of the work's text, the performances most amazingly held my attention; I never even thought of dozing off. I would not exactly call the experience that of listening to music, but rather that of filling myself with the sounds and resonances that floated and flowed around me from all directions. The wonderfully clear solos and choral aspects especially moved me and created lasting impressions that stayed with me long after the performances' ended.

<< A Sad End to a Great Start >>

Sadly, now that the Akiyoshidai International Art Village has been built, I am told that the 1998 International Contemporary Music Seminar and Festival was the last Seminar and Festival that will be planned. But everyone concerned start to grope a next seminor and festival with a new style from 2000. I sincerely hope that some of today's musical artists will be inspired by the hall's uniqueness and create new compositions that will make the most of this very special hall, because there are so few halls designed to match the needs of artists pioneering the genre of contemporary music, and now that Akiyoshidai has such a hall.

Sound Isolation Planning For Concert Halls
Part 2: Isolating and Excluding External Noises and Vibrations

by Satoru Ikeda

One of the most basic requirements of a good hall is the level of quietness achieved in its interior. Many different factors must be addressed to achieve the desired level of quietness, including: (1) isolating external noise and preventing vibration from outside sources; (2) ensuring that sounds do not leak from adjoining or nearby rooms and facilities; and, (3) reducing the level of noise generated by ventilation, heating, and air conditioning equipment. Among these several factors, the first order of workings is the isolation and elimination of external noise and vibration. In today's world, our means of transportation surround us with noise and vibration. The airplanes overhead, trains traveling both above and below ground, and automobiles, trucks, and buses may be necessary conveniences, but we don't want to hear or feel them while enjoying a musical concert. Likewise, the sirens of fire engines and lively bells, whistles, and horns of schools and other institutions are unavoidable in daily life, but must be kept out of the earshot of hall audiences.

Because the isolation of external noise and vibration is essential to constructing a successful hall, one of the first and most critical steps in a project is evaluating and enumerating in full detail the noise and vibration characteristics and patterns of the chosen site, including the sources of the noise and vibration, their variety and loudness or strength, and under what conditions these undesirable "interlopers" appear. In particular, it is important to accurately assess whether the noise in the site's environment is accompanied by vibration, since the propagation of noise and vibration, as well as the measures for isolating the one and the other are substantially different. The treatment of noise and vibration issues impacts the placement of the hall on the site grounds, as well as structural planning, construction methods, cost calculations, and even how long the hall's construction will take to complete. Certainly, when the structure to be built is a concert hall, the most rigorous standards of quietness are required, and the acoustician must survey the site first-hand at the very outset of the project's planning process.

<< Past and Present Trends in Site Locations >>

In the past, most cultural facilities were planned at sites with comparatively quiet surrounding environments and minimal vibration issues. This happy circumstance was probably due less to coincidence than to the intended cultural uses of the projects. Even when the facility combined the multi-functions of governmental and cultural facilities, the areas for each of these purposes would usually be segregated in separate zones of the structure.

However, in order to make halls easily accessible to people during the evening hours when most concert performances are held, today's halls must be located in good proximity to a variety of transportation options. Recent projects also often include the nearby construction of related facilities to provide amenities to both the hall's audiences and to performers and event participants. In Japan, where the cities have severe space limitations, multipurpose revitalization projects for neighborhoods surrounding commuter train stations have resulted in the construction of now ubiquitous "Eki-mae" complexes. These are buildings that contain both shopping and office facilities as well as a multipurpose or concert hall. They are often built literally on top of a train station or immediately adjacent to it. In more rural areas, where automobiles are the primary means of transportation, projects often rise like phoenixes on the half-abandoned "Eki-mae" areas in front of old Japan Railroad stations. These halls sponsors hope to breath life into once bustling town hubs by attracting people with the appeal of a new cultural venue.

<< Noise Isolation in a Hall-friendly Site Location >>

When a hall is constructed in the relatively quiet environment of a large park, most of the external noise is caused by motor vehicle traffic from nearby thoroughfares. In this kind of situation, the volume of external noise that must be isolated from the hall is in the range of 50 - 60dB, and an excellent level of quietness can easily be achieved in a reinforced concrete structure that uses concrete of 150 - 200mm thickness. Given these conditions, the typical steps that we would implement to ensure excellent quietness are:

* Arrange a foyer, corridors, and ancillary rooms around the hall to create buffer space so that the walls of the hall are not in direct contact with the exterior walls of the structure.
* Ensure that the exterior walls and roof are constructed of reinforced concrete at least 150mm in thickness.
* In planning the layout of the loading dock, emergency exits, and other entrances and exits, include sound-absorbing entry rooms, corridors, foyers, and similar buffer space, as well as double-doors and other building materials designed with enhanced sound insulation characteristics.
* Prevent noise from seeping into the hall through the ventilation and smoke detection systems by installing appropriate machinery and equipment and by installing sound-absorbing ducts on the ventilation system ducts or sound insulation the exterior covering of the ventilation system ducts.

<< Noise Isolation in More Challenging Site Locations >>

With an increasing number of both urban and rural halls being constructed in locations that are far from the ideal in terms if the site location's noise and vibration levels, the challenges facing acousticians have also increased. In particular, in Japanese cities, the expansion and upgrading of surface level, elevated, and underground rail systems have become so ubiquitous that it might well be difficult to find a site that is not in proximity to one or multiple rail lines.

<< Addressing the Problem of Solid-Borne Sound from Rail Lines >>

The noise and vibration impact of underground rail transportation is sometimes overlooked, perhaps because it is assumed that any adverse influences will be contained underground. However, even if a nearby transit system line does not currently pose a problem for a new hall, in Japan at least, it is important to anticipate and consider the levels of noise and/or vibration that will result from any future changes, additions, or enhancements that are planned for the rail line.

The problem caused by trains or underground railway lines passing near a hall is not the discomfort of vibrations felt as actual shaking. Rather, the problem arises because the train's vibrations register in human ears in the form of noise. We all experience this conduction of sound waves through solid matter when we stand in an underground train station waiting for a train to arrive: it is that deep monotone rumbling sound that accompanies the mechanical sounds announcing a train's imminent arrival. The audibility of this kind of noise in a hall creates a somewhat insurmountable problem. While steps can be taken to try and reduce the effects of this noise, at present these produce only limited results. In addition, even with special noise isolation treatment, it is difficult to predict with precision how effective the techniques will be and the scope of the work required may be grander in scale than is warranted by the project.

In order to try and minimize the affects of noise from passing rail transit vibrations, changes can be made to lessen the noise in the location where it is created, or at a point in the path of conduction of the noise between its source and the hall, or at the hall itself. Unfortunately, reducing vibrations at any of these points can conflict with measures intended to ensure safety during earthquakes, and can also be affected by the level of precision that is realistically achievable in the building's construction. To date, we have achieved noise reductions of approximately 15dB when employing just one method for reducing this kind of noise. Depending on the circumstances of the location and the desired characteristics of the hall, multiple noise isolation techniques may be implemented to more substantially reduce transit system noise.

One basic approach is to reduce the vibrations that generate the noise at their source. In Japan, which has a highly evolved railway transportation network, yen are being invested in the research and development of reduced-vibration railway tracks and equipment. The organizations that operate and oversee rail transportation can be urged to install this kind of equipment, but eliciting support for such changes is never easy.

Therefore, the most realistic approach is to construct anti-vibration walls and use anti-vibration structural designs in the area between the source of the vibrations and the hall, and to implement a box-in-a-box or so-called "floating" structural design for the hall itself, so that it will be minimally affected by external vibrations. These are all large-scale techniques and their costs can be prohibitive. Hall sponsors understandably want assurances that implementing these acoustical prescriptions is both essential and will ensure the hall's freedom from vibration-related noise. At present, we strongly advise our clients to implement these measures if the hall is within approximately 50m of a rail transit line. If the hall will be built within 10 - 30m of rail transit, we consider implementing one or more of these isolation measures absolutely essential to the success of the project.

<< Addressing the Problem of Airplane Noise >>

One of the major sources of air-borne sound in the absence of vibration, issues is aircraft flying over the hall site. In the entire history of Nagata & Associates projects, only one has ever faced a noise isolation issue as loud and difficult as dealing with rail lines. That project was a concert hall constructed near a military base. In this unfortunate situation, while we knew with certainty that there would be noise from aircraft departing and returning to the base, it was virtually impossible to precisely measure the volume of the noise or the specific circumstances and details of when the noise would occur and whether it would vary in volume and other characteristics. At its worst extreme, we measured a noise level of 104 - 109dB(A). For this concert hall, we proposed noise isolation treatment sufficient to isolate more than 75dB (at 500Hz) and more than 80dB when lower register noise was factored into our calculations.

In this concert hall project, our first instincts were to design a sound insulation layer inside the hall structure. However, the design of the hall's stage area included complex functionalities and was designed to be built using "floating" construction. When we considered these factors, we adopted an alternate, "double protection" plan. In this solution, we added poured concrete panels of 150mm to the hall's reinforced concrete exterior, and we also added anti-vibration reinforcing to the concrete poured at the hall's site. By covering the hall's roofing and all of the hall's exterior walls with the anti-vibration concrete, we created a sound insulation layer over the framework's entire exterior. In thinking about this solution, it may be helpful to imagine anti-vibration-treated precast concrete panel being added to the exterior framework of the reinforced concrete in a kind of curtain-wall manner. Since our response to the noise of aircraft flying nearby required extra work on the entire exterior, including the hall's roof, as well as immense space for the stage's floating construction, the efficacy of these isolation techniques and their adoption became the object of major discussions and decisions in the planning and execution of this concert hall.

<< In Summary >>

As exemplified in the above solutions to noise and vibration problems, while it may at first seem desirable to build a tightly-packed building layout so as to maximize a hall's use, compressed use of a location's space may not be the right answer to a hall's noise and vibration isolation needs. Luckily, when the project is the kind of multifunctional facility that is becoming more and more popular, we can achieve desirable levels of sound insulation between individual rooms by applying some of the same measures that we have adopted in the examples and other projects to isolate noise and vibration at the structural level for entire buildings.

Sound Bites: The Musical Toy You Hear in Your Mouth

by Laurie Holtzberg (Nagata Acoustics News translator)

Sound Bites
One morning this past June, as my car sat stuck in the Bay Bridge commute traffic and I listened to a popular FM radio station to get myself ready for the day ahead, I wondered about an appropriate "American" souvenir to give my friends at Nagata Acoustics when they visited San Francisco on their way back from the 16th International Congress on Acoustics being held in Seattle. Suddenly, the radio announcers began talking excitedly about Sound Bites, a new invention that, they said, "delivers sounds inside your head." As soon as I heard that Sound Bites is both a candy and a toy, and that it combines the principle of conducting sound waves with modern technology, I knew I had the answer for my souvenir quandary.

Available at local toy stores, Sound Bites is a brightly-colored, battery-run, plastic toy that sends safe sound vibrations through a standard lollipop. When a person bites on a lollipop that has been inserted into a Sound Bites holder, sound vibrations travel through the teeth to the inner ear, where they are heard just like normal sounds. While the music produced by the Sound Bites holder is barely audible before the one bites the lollipop, once your teeth are on the lollipop, you can hear the music loud and clear, but the source of the sound seems to be inside your own mouth. The effect is unlike any other, and the fun is enhanced by buttons on the Sound Bites holder that allow one to vary the tune as if playing a wind instrument.

Sound Bites was developed by two San Francisco Bay Area residents, David Capper and Andrew Filo, who together founded Sound Bites, LLC, a subsidiary of the U.S. toy manufacturer, Hasbro, Inc. Aimed primarily at youngsters, the Sound Bites holder comes in three musical varieties: Rockin' Guitar, Rockin' Drum, and Rockin' Saxophone, as well as three special effects versions. A big hit this summer in the United States, worldwide sales of Sound Bites will begin in 1999.

Andrew Filo, who is a holder of 13 U.S. patents, was inspired to create Sound Bites by his knowledge that Thomas Edison, who was nearly deaf, had designed a bite bar to enable him to hear the sounds of his phonograph through his inner ear. Filo is a prolific inventor, and he divides his time between inventing serious rocket science devices for such companies as McDonnell Douglass and devising more fun stuff and toys, including the new Sound Bites musical candy toy.

When I presented the Nagata Acoustics' acousticians with Sound Bites -- still wrapped in its packaging with two lollipops and a battery -- it took them almost no time at all to guess how the toy works. Then, with their own scientific minds, they proceeded to conjecture other applications bordering on scientific fantasy, and they asked me to step out from behind the scenes to write about this fun American toy that lets us experience sound waves in an unusual way.

Knowing how innovative Nagata Acoustics can be, I can only guess where my innocent gift-giving might lead. Perhaps someday, with a different computer chip, a set of false teeth made with reverberation-enhancing materials, a sound-conducting d enture adhesive, and Nagata & Associates' expertise . . .

Nagata Acoustics News 98-9iNo.129j
Issued : September 25, 1998

Nagata Acoustics Inc.

E-mail: info@nagata.co.jp

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