Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 13-09 (No.309)

Issued : September 25, 2013

[ Japanese Version ]

A New Cultural Center Opens in Akiha Ward, Niigata City

By Ayako Hakozaki

Akiha Ward Cultural Center Building Exterior
Akiha Ward Cultural Center Building Exterior

The exposed concrete structure of the new Akiha Ward Cultural Center curves gently into a rising spiral, complementing the surrounding green trees and plants. The architectural inspiration for the new building comes from the Japanese concept of "satoyama", a natural environment of woodland that exists with moderate intervention of human beings.

Akiha Ward Cultural Center celebrates its opening concerts this month. It is Nagata Acoustics' third cultural center project for Niigata City Wards. The other two projects were the cultural centers of Kita Ward and Konan Ward (discussed in the July, 2010 issue and the November, 2012 issue of the Nagata Acoustics Newsletter).

Chiaki Arai Urban and Architecture Design served as the project architect for Akiha Ward Cultural Center. We have collaborated as the acoustical consultant on projects designed by this architect many times in the past and the Akiha Ward project marks our 10th new construction project with this architect. (We have also worked with this architect on a number of renovation projects.) During the construction phase of each project with Chiaki Arai Urban and Architecture Design, I invariably find myself surprised and marveling at how the design develops. I again experienced the same surprise, wonder and appreciation on this project.

The construction work for this project was accomplished by a joint venture of 3 companies: Taisei Corporation, Tanaka Kensetsu Kogyo and Shinko Construction.

<< Overview of the Center's Facilities >>

Floor Plan of First Floor
Floor Plan of First Floor

Akiha Ward Cultural Center has a 496-seat multipurpose hall for music and theater performances as well as two practice rooms and a studio. The building also has support spaces such as meeting rooms and lobby area. In the nearly circular footprint of the building, the hall is located in the center and the practice rooms and other spaces are placed around the hall's perimeter.

<< Sound Isolation Design >>

A key objective of the project's sound isolation design was to enable simultaneous use of the Akiha Ward Cultural Center's hall, practice rooms and studio. To achieve this goal, each of these rooms required a high level of sound isolation performance.

The layout planning of the cultural center enables the large practice room to be used as an extension of the multipurpose hall by locating the large practice room behind the multipurpose hall's stage. This practice room is only separated from the multipurpose hall by a corridor.

By contrast, we were able to locate the small practice room and studio at considerable physical distance from the multipurpose hall. In addition, these two rooms are separated from the multipurpose hall by dressing rooms and other support spaces that provide an acoustical buffer between the small practice room and studio area and the multipurpose hall.

We adopted anti-vibration and sound-isolating structural designs for both of the practice rooms and the studio to achieve the needed sound isolation performance levels for simultaneous use of all of the rooms.

<< The Multipurpose Hall's Room Acoustical Design >>

Multipurpose Hall Interior
Multipurpose Hall Interior
Multipurpose Hall Interior

One of the distinguishing features of the multipurpose hall is the multifaceted concrete structure of its walls and ceiling around the audience seating area. Within the many facets are cut-outs in the concrete that the architect specified for design reasons and that we used to acoustical design advantage by installing construction materials.

With concrete surfaces being the majority of the multipurpose hall's surface area, our room acoustical design necessarily focused on controlling the lower sound ranges and preventing long-path echoes from the rear part of the walls to the stage and front portion of the audience seating area. From the interior of the hall, all of the wall and ceiling cut-outs are covered with 1.5 mm (0.06 in)-thick, thin sound-absorbing aluminum fiber panels. The panels above and around the front and center portions of the hall are backed with drywall and, as a result, these panels have approximately the same sound absorbing characteristics as drywall, except that we added glass wool behind the drywall panels to increase sound absorption of lower frequency sounds. In addition, we installed glass wool directly behind the aluminum fiber panels at the rear of the hall to create surface areas that achieve an even greater sound absorbing characteristic.

While we used the wall cut-outs to create sound absorbing surfaces on the otherwise entirely rear concrete walls of the hall, these sound-absorbing surfaces alone would be insufficient to prevent echoes. Therefore, around each of the cut-outs we placed visually appealing panels designed with the imagery of wing-like extensions. These panels are made of a sound-absorbing aluminum fiber material backed by glass wool and serve as additional sound absorbing surfaces.

In addition, to soften the otherwise sometimes harsh reflections from concrete surfaces, we specified that the exposed concrete have a textured finish. As a result of our design decisions, the hall's lower frequency sounds have rather long, yet natural-sounding reverberations. Also, after the hall's completion, we confirmed that it is successfully free of echoes.

Entrance Lobby
Entrance Lobby

<< Sound Absorption Finishes for Common Areas >>

In general, in the parts of a building like Akiha Ward Cultural Center that are not specific rooms for music practice or performance, it is easy to recognize the need to control too long acoustical reverberations and prevent the undesirable transfer of noise to other spaces. However, finding sound absorbing materials that blend and complement the architect's intentions for these spaces is often a difficult challenge.

For this project, we adopted the use of circular modular units of perforated metal set into frames. We installed this material for the ceiling of the small practice room and studio and also for the ceilings of the entrance lobby and foyer. In locations where we wanted to add a sound absorption characteristic, we installed glass wool above the perforated metal modules. This ceiling solution is a good example of a design that answers both the visual needs of the architect and the acoustical objectives.

The website for the Akiha Ward Cultural Center is available in Japanese.

"Stage Technology Seminar 2013" at New National Theatre, Tokyo:
Three Sessions, Including My Presentation on Stage Curtain Materials

By Makoto Ino

Loudspeakers set up on the Playhouse stage during
Loudspeakers set up on the Playhouse stage
during "Stage Technology Seminar 2013"

On July 30, 2013, I attended and spoke at the second session of "Stage Technology Seminar 2013", held at New National Theatre in Tokyo. The seminar was sponsored by New National Theatre with the cooperation of the Stage Technology Professionals of Public Halls Liaison Group, the Theatre and Entertainment Technology Association of Japan and the Stage Sound Association of Japan. About 60 professionals, including the technical staff of New National Theatre and other companies, attended the seminar in the theatre's Playhouse.

At the start of the seminar, New National Theatre Senior Technical Manager Mr. Hisayuki Ito addressed the gathering. He mentioned that this year's seminar on acoustics is the second seminar the theatre has hosted for stage technology professionals and he recalled the success of the first stage technology seminar held last year on the topic of stage lighting and video technologies. Mr. Ito told us that the goal of these seminars is to provide knowledge and demonstrate technologies on-site in a hall environment. Also, he encouragingly shared that he and the theatre plan to continue holding these seminars in future years.

<< Session 1: Point Source vs. Line Array Loudspeakers >>

After Mr. Ito's opening remarks, New National Theatre Sound and Video division's Manager Mr. Kunio Watanabe presided over the seminar's three sessions. The topic of the first session was differences between point source and line array loudspeakers. The session presenters explained the different configurations used with each of the two kinds of speakers and installation differences between systems using one or the other kind of speakers. The session's presenters set up and demonstrated both types of speakers during the session so that the audience could see the differences being discussed and hear the two kinds of speaker model systems in the Playhouse.

With the increased availability and use of line array loudspeakers we typically use the phrase "point source loudspeaker" when comparing line array speakers to any single unit or full-range type of loudspeaker. However, it is worth mentioning that instead of being a precise technical term, "point source speaker" is more of a layman's catch-all term for speakers that are not line arrays.

Mr. Takahiro Tano of audio equipment vendor ATL, Inc. explained the differences between the sound emission characteristics of point source and line array loudspeakers. In particular, Mr. Tano focused his talk on the sound distribution properties of multiple-unit line array speaker installations and how distance from the units affects the speakers' specific distribution properties.

After speaking to the group about these differences, Mr. Tano demonstrated the set-up arrangements and combinations of several loudspeaker systems and provided the audience the opportunity to listen to each of these different configurations. He compared a setup of loudspeakers suspended above the center of the stage to a ground stack setup at the left and right sides of the stage. Also, for the ground stack setup, he demonstrated the use of large, medium and small-sized units of both point source and line array models.

I felt that as I moved away from the line array units the clarity of sound improved. When listening to the point source models, the larger the model the more completely did the sound volume fill the room. I did not hear any qualitative differences among the demonstrated three sizes of point source models. In the case of the line array speakers, the larger the units, the clearer they sounded, which I think was due to the use of 2-way speakers vs. 4-way speaker units.

<< Session 2: How Different Materials Used as Stage Curtains Affect Loudspeaker Sound >>

Session 2: Real-time Tests Demonstrating How Different Materials Used as Stage Curtains Affect Loudspeaker Sound (Photo Courtesy of Stage Sound Association of Japan)
Session 2: Real-time Demonstration
(Photo Courtesy of Stage Sound Association of Japan)

Loudspeakers are typically considered to be unsightly distractions on and around the stage. Often, a hall addresses this situation by hiding the speakers behind some kind of curtain material. As the presenter at the seminar's second session, I began by briefly summarizing the characteristics of sound absorbing and sound isolating materials and their effect on sound. After providing this overview, New National Theatre Technical Designer Mr. Hiroto Konishi joined me on stage for a question and answer conversation about the curtain materials at New National Theatre and how he uses these curtains. During our conversation, we used the Playhouse's curtains and loudspeakers to demonstrate the effect of curtain materials on reproduced sound.

The Playhouse has both a PVC screen that rises vertically and a grand drape front curtain. In addition, for this seminar Mr. Watanabe provided 15 samples of other fabrics used for stage curtains, including georgette, canvas, burlap, felt and velveteen. We successively draped each of these materials in front of the loudspeakers and played music, speech and sound effects through the speakers. In addition to giving seminar participants the opportunity to listen to how the sound changed under each of these conditions, we measured the frequency responses of each condition in real time and projected the results on a screen for the participants to see while listening to each demonstration.

As might be expected, the fabrics made with a relatively open weave such as georgette, burlap and felt only slightly affected the sound frequencies and minimally reduced the local sound level. These fabrics could be considered to have virtually no effect on the overall quality of the reproduced sound. By contrast, among the fabrics made of synthetic materials, the denser the material, the more it caused attenuation of high frequency sounds and the more the material altered the overall quality of the reproduced sound.

I also did a simple experiment with each of the fabric samples used in the presentation. I held each sample to my open mouth and exhaled. The better the acoustic transparency results for a fabric, the easier it was for my breath to pass through the material. I concluded my presentation with a summary of the demonstration results which showed that open-weave, thin, natural materials such as linen and cotton are to be preferred for stage curtains used in front of loudspeakers to hide them from view.

<< Session 3: New Product Introductions >>

The first part of the seminar's third session introduced new sound field correction device equipment that uses finite impulse response (FIR) filter technology. Tokyo Metropolitan Theatre's Mr. Koichi Ishimaru served as moderator and representatives of two vendors explained the use of this new technology. Mr. Shinichiro Kaneko represented Yamaha Sound Systems Inc. and Mr. Motoo Izawa represented EVI AUDIO Japan, Ltd.

In the past, equalizer devices only corrected for the amplitude characteristic of frequencies. The new devices that use an FIR filter can also correct for frequencies' phase characteristic and this minimizes the degradation of the transferred sound. That is, the new devices apparently negate several of the causes of degraded sound quality.

In practice, I found that adding an FIR filter to a sound system that has sound-impacting stage curtains draped in front of its loudspeakers reduces the change in sound quality caused by the curtains. FIR filters have strong effectiveness, and the key to widespread adoption of this technology probably depends on whether technical professionals will be able to use their listening skills as the means to appropriately adjust the filters in the field so that they perform as desired.

For the second half of the third session, New National Theatre's Mr. Watanabe and Mr. Tomohiro Hasebe of stage sound and lighting vendor LIVEGEAR Corporation jointly presented a demonstration about the use of compact line array loudspeakers. They attached units of the speakers to the Playhouse's banisters and filled the stage with a row of the small units. The seminar participants were then treated to an unexpected listening experience. The setup created a wonderful yet somewhat bewildering experience of hearing sound without being able to tell the direction of the sound's source. I'm sure that not being aware of the location of the sound source can be a very desirable effect for some productions and situations.

<< More Research Needed >>

Of the three sessions, the first session left me thinking of one very specific area that would benefit from additional research. In comparing the output of line array and point source loudspeakers, I think we can generalize that the line array models have better clarity of sound while the output of point source loudspeakers sounds more natural. I believe there would be good value in exploring the reasons for these differences between the two kinds of speakers.

My Visit to Hollywood Bowl

By Nobuhiko Hattori

At the end of this past June, Nagata Acoustics' Los Angeles Office held a workshop on stage sound systems. The week-long event included study groups and discussions as well as visits to various venues and on-location demonstrations and listening opportunities. In this article, I will report on my visit to the Hollywood Bowl.

<< Hollywood Bowl's Special Location and New Loudspeaker System >>

The Stage
The Stage

The open-air Hollywood Bowl opened in 1922 in the Hollywood area of Los Angeles with a seating capacity of more than 17,000 seats. This amphitheater benefits from the natural beauty and concave shape of the hillside where the venue sits. Hollywood Bowl has a very large seating area of elliptical shape with a distinctive, quarter-circle "shell" stage acoustical system at one end of the venue's egg-like shape.

Hollywood Bowl replaced its loudspeaker system in the spring of 2013. The new system including L-Acoustics' K1 units, has been installed as three large units suspended at the front of the shell.

<< The Annual Summer Season Opening Night >>

Every summer, Opening Night at Hollywood Bowl is a special gala, typically replete with fireworks as it was this year. During the three summer months beginning in June and into September, the Los Angeles Philharmonic makes Hollywood Bowl its home venue. A concert by the orchestra, guest artists, related performing groups or others takes place almost every summer night. The calendar's fare ranges from the Los Angeles Philharmonic and Hollywood Bowl Orchestra (HBO) to jazz, R&B artists, musicals and a variety of other musical genres.

Audience patrons often arrive hours before concert start times to enjoy picnic dinners in the hills above the "Bowl", as the venue is affectionately called by Angelinos. Groups large and small fill the picnic tables and tree-shaded lawns, creating a festive pre-concert atmosphere.

This year, Opening Night took place on June 22. In addition to large fireworks, six groups of performers each took their turn on stage interspersed by presenters who introduced this year's hall of fame inductees: Aerosmith's Steven Tyler and Joe Perry, Patti Austin and John Legend. Other participating artists included the HBO and Youth Orchestra Los Angeles (YOLA) conducted by Thomas Wilkins, Stevie Wonder, Darren Criss, Arsenio Hall and host Angela Bassett.

<< Experiencing the New Loudspeaker System >>

Looking at the huge loudspeakers that face the audience, I imagined that they would emit not just large volume but also harsh sound. Instead, even in the seats near the stage, the sound had appropriate loudness with good sound quality. In particular, the most memorable moments listening through these speakers came when I listened to John Legend's presenter, Stevie Wonder, with his powerful voice and long sustained, high tones.

Dinner before the Performance
Dinner before the Performance

Before the start of the concert, I was treated to a tour of the sound control booth by Hollywood Bowl Sound Designer Fred Vogler. Mr. Vogler showed me the height adjustable booth with rise-and-fall floor system and details of the mixing equipment and the Bowl's other sound system devices. On June 22, I had just arrived in the U.S. and by the end of the evening I'd been awake some 20 hours, but any sleepiness I might otherwise have felt vanished amidst the excitement of the Opening Night and the valuable opportunity to experience up close Hollywood Bowl's new loudspeaker system.

Nagata Acoustics Inc.

(Tokyo Office)
Hongo Segawa Bldg. 3F, 2-35-10 Hongo
Bunkyo-ku, Tokyo 113-0033, Japan
Tel: +81-3-5800-2671, Fax: +81-3-5800-2672

(LA Office)
2130 Sawtelle Blvd., Suite 308
Los Angeles, CA 90025, U.S.A.
Tel: +1-310-231-7878, Fax: +1-310-231-7816

(Paris Office)
75, avenue Parmentier
75011 Paris, France
Tel: +33 (0)1 40 21 44 25, Fax: +33 (0)1 40 21 24 00

E-mail: info@nagata.co.jp

[ Japanese Version ]