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



Nagata Acoustics News 06-10 (No.226)
Issued :October 25, 2006



Recalling Prof. Yasuo Makita's Contributions to the Discipline of Acoustics

by Dr. Minoru Nagata, founder of Nagata Acoustics

As I sadly reported three months ago, in the July edition of this newsletter, Professor Yasuo Makita passed away on May 12, 2006. He was 93 years old, and had such insightful and comprehensive knowledge of sound and acoustics that I wish I still had the opportunity to be taught by him.

Prof. Makita began his professional career, before World War II, at the Aeronautical Research Institute of Tokyo Imperial University (today's University of Tokyo). After the war, he held a professorship at Osaka University until he left academia in 1951 for a position at NHK Technical Research Laboratories. At NHK, Prof. Makita's first position was chief of the Architectural Acoustics Research Group. Later, he was promoted to Manager of the Acoustical Department, then to Director of NHK's Broadcasting Science Laboratories. Throughout his years at NHK, until his retirement in 1968, he mentored other researchers and acoustical engineers, providing advice on the content of research topics and research methodologies, as well as direction on how to write and compile scientific papers and reports.

In 1968, Prof. Makita returned to academia, participated in the founding of Kyushu Institute of Design (Kyushu Geijutsu Koka Daigaku), and was instrumental in this institution becoming the first Japanese national university to offer a curriculum specifically focused on acoustical design. Also in 1968, the school appointed him to the rank of full professor in the discipline of acoustical design and he continued to teach and nurture the individual strengths and capabilities of all who studied with him, until he reached the age of mandatory retirement in 1978. Today, many of his former students are leading professors and acoustical engineering practitioners in a range of acoustical engineering specialties and related disciplines.

Prof. Makita's instruction and guidance covered a great range of subject matter, and now that he is gone, I am sure that his other former students pause frequently to remember and deeply appreciate how much we learned from him, as I often do. Because of this great legacy, it is all the more surprising to realize the relatively few technical advances and publications that bear his name. After gathering together the few pieces of his work that I already had at hand, and with the help of our colleagues from NHK Technical Research Laboratories and some of his Kyushu Institute of Design students, I assembled this list of his writings and publications, together with some background notes.

During World War II, Prof. Makita worked in a department of the Aeronautical Research Institute of Tokyo Imperial University led by a Professor Obata. Prof. Obata had a reputation for being a strict instructor who would critique even the smallest details of students' draftsmanship. Prof. Makita never spoke to me about the research he did during this period. He was employed by an educational institution, but this was an era when war cast a wide shadow, and I know only that during this period Prof. Makita authored three papers on the auditory faculty that were published in the Journal of the Acoustical Society of Japan.

Around the time that Prof. Makita joined NHK Technical Research Laboratories, stereophonic sound was the big topic causing much excitement in the world of acoustics. Prof. Makita focused his research on one stereophonic effect, the directional localization of sound, and after determining through analysis that a sound image in a stereophonic sound field is localized to the normal direction of wave front, he devised a way to prove his analysis experimentally. Also during this period, Prof. Makita conducted research on room conditions for the reproduction of sound recorded using two microphones. He delivered the results of his research at the 12th technical meeting of the European Broadcasting Union (EBU) and, thereafter, published his paper in the EBU Review. This was the first paper to offer an analysis of stereophonic sound fields and it was also Prof. Makita's first participation in a professional meeting outside Japan.

As I mentioned in my July article, the two Japanese halls built under Prof. Makita's guidance, namely Shinbashi NHK Hall and Tokyo Bunka Kaikan, became the main stages on which Japan's classical music concert industry grew and was sustained for several decades. Significantly, it was also through the building of these two halls that the content and process methodology of Japanese acoustical design solidified and established best practice standards. Prof. Makita wrote about the acoustical design of Shinbashi NHK Hall in his volume Architectural Acoustics, and he was the executive editor of NHK Technical Research Laboratories' book, The Acoustical Design of Tokyo Bunka Kaikan. The earlier work, Architectural Acoustics, covers fundamentals of architectural acoustics and acoustical design from the wave theory to the specifics of room acoustical design, becoming the first architectural acoustics textbook written in the Japanese language. Similarly, by including every aspect of the project's planning, design and construction in The Acoustical Design of Tokyo Bunka Kaikan, Prof. Makita produced Japan's first guidebook that provides a complete outline of the steps, topics and reference materials needed for acoustical consultants to understand, plan, create and execute an acoustical design within the flow of a construction project.

When direct sound is propagated in the sound fields of a room, it is normally accompanied by many sound reflections. In acoustical engineering research, the ultimate sound field in a room is known by the term "sound diffusion." Through research into the nature of sound diffusion, reverberation theory developed, and this theory has made large contributions to the practice of acoustical room design. However, other phenomena, of which sound absorption is one example, exhibit real properties that cannot be explained by reverberation theory. Prof. Makita found this unresolved, ambiguous topic irksome and he could not resist tackling it. Positing a material with a boundary layer of minimal thickness on its surface and a mediating layer, and drawing on the kinetic theory of gases, Prof. Makita revised the accepted cosine rule for oblique incident sound absorption in diffused sound fields and published his revisions and later examinations in the journal Acustica, the Journal of the European Acoustics Association.

In his papers on stereophonic sound fields and the cosine rule revision, I sense the joy with which Prof. Makita surely researched, solved and wrote about these technical subjects.

During the period of more than 10 years that Prof. Makita spent at NHK Technical Research Laboratories, the lab rose to a position of technical leadership in Japan in the field of acoustical engineering, pioneering practical advances through research and pursuing innovative topics and inventions. However, Prof. Makita did not proactively involve himself in practical applications of his discipline. To my knowledge, his chairmanship of the Japan Standards Association's general research initiative for the creation of JIS industry standards was his only direct active participation in formulating day-to-day acoustical engineering practices.

As I look back over my years of association and friendship with Prof. Makita, I cannot help but recall with regret a number of opportunities he placed before me that I did not have the genius to bring to fruition. He always taught us from the heart to direct ourselves to the essence of our subject matter and be philosophical in our thinking and in our actions, and he modeled these precepts for us in all that he did and accomplished.

List of Prof. Makita's Writings and Publications * In Japanese only. The titles were translated into English by Dr. Minoru Nagata.

Aomori Museum of Art - Contrasts of White and Clay

by Dr. Keiji Oguchi

Fig.1 Exterior view
Courtesy of Aomori Museum of Art
Photo by Daici Ano
An acoustical consultant can be a valuable participant on an art museum construction project. For example, the appropriate level of quietness in the exhibition space can be realized through noise control engineering or the museum plans may include an auditorium and a goal of intelligible amplified sound, so that the expertise of an acoustical consultant is needed to create the room acoustical design.

The topic of this article, the new Aomori Museum of Art, includes a theater for audio-visual screenings, drama performances and lectures, and also has a studio space where video content will be recorded as well as shown to audiences. Nagata Acoustics served as the acoustical consultant for the acoustics of these two rooms of the art museum project. Mr. Jun Aoki created the museum's architectural design. Nagata Acoustics has collaborated with Mr. Aoki on numerous projects since he led Isozaki Atelier's design of Art Tower Mito in 1990.

<< The Museum Theater >>

Fig.2 Theater
Photo by Tsunejiro Watanabe
The most famous acquisition in the museum's collection is, without question, the museum's three Chagall Ballet Aleko backdrops. The Russian-born artist created the backdrops while in the United States, to which he fled from France during World War II to escape the Nazis. Each of the backdrops measures 15 m. (49.2 ft) wide by 9 m. (29.5 ft) high. They are permanently installed in the building's Aleko Hall, which rises through all four stories of the structure. Aleko Hall measures 21 m. (69 ft) wide by 21 m. (69 ft) long by 19.5 m. (64 ft) from floor to ceiling.

The front wall of the museum's theater is a shared wall between the theater and the large Aleko Hall. This shared wall slides up and down, so that Aleko Hall can be made visible to the audience in the theater. The theater is located on the museum's ground floor, while Aleko Hall traverses all of the building's levels, from the lowest B2 level, through B1, first (ground) and second floors, so the theater level is approximately 7 m. (23 ft) above the floor of Aleko Hall. Seen from Aleko Hall, the sliding wall between hall and theater appears very large, as it measures 16 m. (23 ft) by 16 m. (23 ft).

When the sliding wall is closed for an event in the theater, the museum needs the wall to provide sound isolation between the theater and Aleko Hall. Our design achieves sound isolation for greater than 60 dB (at mid-range frequencies), enabling visitors in Aleko Hall to enjoy the permanent exhibition undisturbed by sound from the theater (extremely loud sounds in the theater excepted). In addition, for visually aesthetic reasons, we were required to develop a design that does not reveal to Aleko Hall visitors that the sliding wall is, in fact, a sliding wall. To meet this objective, we installed all of the sound isolation sealing systems on the theater side of the wall. From the inside of Aleko Hall, only the edge line of the top of the sliding wall hints at its functionality. Our design preserves the desired illusion of a fixed wall and visitors are unlikely to notice that this large wall portion can be moved up and down.

Inside the theater, the interior color scheme uses black and brown everywhere. The walls are finished with acoustically transparent expanded metal, behind which we placed sound absorbing material along the entire wall surfaces. We also placed massive sound absorbing material around the ceiling perimeter above the grid ceiling to control low frequency reverberation. The theater has roomy, well-padded upholstered audience seating and the acoustics are characterized by damped reverberations and a high level of sound clarity.

<< The Museum Studio >>

Fig.3 Studio
Photo by Jun Aoki & Associates
The studio has two intended categories of use: to be a venue for showing films and premiering new audio-visual art; and, to be a location where both soundtracks and visual materials can be recorded. Because the studio will be used for recording purposes, we needed to isolate the studio interior from all external noise and vibration. We adopted a box-in-box design strategy to achieve this objective. The geometrical configuration of the studio's space is a cuboid (a box with six rectangular sides) with the special characteristic that one of the sides is made almost entirely of glass. Under these challenging conditions, we nevertheless achieved sound isolation performance of 80 dB, measured at mid-range frequencies.

Like the museum's theater, the studio features a predominantly black interior. At dispersed locations along the studio walls we installed perforated panel units constructed to absorb sound and achieve the desired objective of suppressing the room's liveliness.

<< Acoustics and Concert Use of Aleko Hall >>

Aleko Hall, with its close to cube proportions, has traditional Japanese "tataki" flooring, a smooth, concrete-like surface made of clay earth combined with coal or other substances and water, and the walls and ceiling are laminated wallboard. These interior finishes result in a space with a long reverberation characteristic.

Nagata Acoustics was not specifically consulted about the Aleko Hall space, and when I had the opportunity to stand in it during a tour of the structure shortly before its completion, I quickly sensed that it would be very enjoyable to hear a concert performed in this high-ceilinged space. Happily, I learned that the museum does have plan for concerts in Aleko Hall. Performances of the entire cycle of Beethoven's piano sonatas began in May and will complete in March, 2007. The museum is also planning performances of dramatic works in the theater. Clearly, this museum aims to produce artistic offerings beyond the exhibitions expected of an art museum.

<< Contrasts of White and Clay and the Museum's Opening Exhibit >>

The Aomori Museum of Art's exterior has a brick curtain wall painted white. The bricks give the white surface a delicate texture that distinguishes this building from structures with smooth-surfaced concrete exteriors. In the museum's exhibition rooms, white finishes contrast with earthy clay coloring. The clay tones give the building a visual connection with the Sannai Maruyama Jomon Era excavation site adjacent to the museum. What I found most striking about the juxtaposition of white and clay coloring is the lack of artificiality. The contrasting colors are used in ways that appear natural and complementary.

Chagall painted four ballet Aleko backdrops. The Aomori Museum of Art owns three, and the fourth (for the ballet's third act) is owned by the Philadelphia Museum of Art in the United States. The Philadelphia Museum has lent the fourth backdrop to the Aomori Museum of Art for its opening exhibit, which lasts to December 2006. There is still time this year to take advantage of the Aomori Museum of Art's opening and the wonderful opportunity to view all four Chagall ballet Aleko backdrops together under the same roof.

The Aomori Museum of Art's English-language website URL is: http://www.aomori-museum.jp/en/

The Institute of Noise Control Engineering/Japan Celebrates 30 Years

by Toshiko Fukuchi

On September 20 and 21, 2006, The Institute of Noise Control Engineering/Japan (INCE Japan) met for its Autumn 2006 Congress at Aichi Institute of Technology in Nagoya, Japan. This year marks INCE Japan's 30th year, and in commemoration of this milestone anniversary, the organizers moved the event from its usual Tokyo-area location to the Nagoya venue. In 1975, the International INTER-NOISE Congress held its fourth annual meeting in Sendai, Japan, and this event led to the founding of INCE Japan a year later in 1976.

At the time that INCE Japan began, Japan was in the midst of rapid economic expansion, and the side effects of air pollution and traffic noise problems were becoming frequent topics of concern in front-page newspaper articles. Against this backdrop, noise control engineering practitioners and government functionaries charged with addressing noise control issues came together as members of this new professional organization with the aim of fostering the implementation of practical technologies and measures to achieve noise and vibration control.

For the 30th anniversary celebration, INCE Japan held an open essay contest for young researchers on "sound environments of the future" and invited the contest winners to participate as panelists in a live symposium on this topic during the 30th anniversary congress. Mentally fast-forwarding themselves to a Japan 50 years in the future, and focusing on the Japanese traffic conditions they might then encounter, the panelists presented and debated their ideas on noise control problems, accessibility needs for seniors, prospects for the use of soundscapes and information sharing benefits and concerns. The unconventional concepts expressed by the youthful panelists met with some warnings and cautionary comments from veteran conference attendees, leading to a lively, yet collegial, symposium event.

Compared with the level of quietness the average person desired or accepted just a few years ago, it seems that today people want a considerably quieter environment. Nevertheless, at local shopping and business districts, noise proliferates as much as at any time in the past. Calculating noise values no longer suffices; instead, researchers and community residents alike call for studies of the psychological and physiological impacts of noise. The discipline of noise control engineering has many problems left to solve and the valuable role the INCE Japan plays will likely continue for many years to come.

INCE Japan English-language website URL is: http://www.ince-j.or.jp/ENG/english.html

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Nagata Acoustics News 06-10 (No.226)
Issued : October 25, 2006

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