Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 14-01 (No.313)

Issued : January 25, 2014

[ Japanese Version ]

New Hall for Central Conservatory of Music in Beijing

By Dr. Keiji Oguchi

Exterior view of the new hall
Exterior view of the new hall

Interior view of the new hall
Interior view of the new hall

At Beijing's Central Conservatory of Music, construction of the conservatory's new hall is progressing well. The Beijing firm Walton Design Consulting Engineering Co., Ltd is the project architect and Nagata Acoustics serves as the acoustical consultant for the new hall.

<< Overview of the Central Conservatory of Music >>

The Central Conservatory of Music was founded in 1950 in Tianjin. The establishment of the Central Conservatory merged together with the National Conservatory of Music, the Peking National School of Fine Arts and other 6 departments of music in Universities from 1920s to 1940s in China. In 1958, the Central Conservatory relocated to Fuxingmen in Xicheng District, Beijing (the birthplace of Qing Dynasty Emperor Guangxu) where the school remains to this day.

Majors offered at the Central Conservatory span a wide range of musical disciplines including, among others, music composition, conducting, performance (string instruments, wind instruments, percussion, piano and voice), Chinese music performance specializations in both traditional Chinese instruments such as the zheng (Chinese koto), pipa (Chinese lute) and erhu (a two-stringed instrument), and music education, modern electro-acoustic music and even violin-making and restoration. In 2013, the school had more than 350 professors and instructors teaching a student body of nearly 2,000 students.

<< Background to Nagata Acoustics' Participation on the Central Conservatory of Music Project >>

Nagata Acoustics' connection with the Central Conservatory of Music project began with my first visit to the school about 18 months ago in June, 2012. The visit came about because of my advisory work on the Tokyo Geijutsu Daigaku (Tokyo University of the Arts) remodel project that is currently in progress. That project, expected to be ready for the new Japanese school year that will start this April, involves a total renovation of the campus' Building 4-including significant sound isolation upgrades-and a renaming of the facility to "International Performing Arts Advanced Research Square".

One of Tokyo University of the Arts' project committee members, Prof. Toru Kamekawa, of the Department of Musical Creativity and the Environment, received a request from Mr. Wang, who teaches a modern electro-acoustic music course at Central Conservatory of Music, regarding a project at the conservatory for the renovation and new construction of a recording studio. Mr. Wang knows Prof. Kamekawa because the former previously spent time in Japan as a foreign exchange student in Prof. Kamekawa's research group. At the invitation of Conservatory, Prof. Kamekawa and his colleague Dr. Nakahara made plans to visit Beijing and meet with Mr. Wang. The timing of their visit by Prof. Kamekawa and Dr. Nakahara coincided with a visit I planned to make to China and I asked if I might join their visit and they agreed to include me. I hoped that by visiting the conservatory I would gain insight into the kind of buildings and facilities that the conservatory provides for its students.

When I attended the meeting with Mr. Wang, I learned that his studio project is part of the larger construction project for the conservatory's new hall. Construction had already begun on the structure of the new building, but the room acoustical design had not yet begun. (In Japan, our projects typically prepare the interior fit-out design before construction of the structure starts. In China, construction of the structure begins as soon as that part of the project's structural design has completed.) At that first visit the Conservatory, I extemporaneously presented an overview of Nagata Acoustics' consulting services. This presentation led us to be invited to the competition of acoustical consultant selection for the new hall and finally Nagata Acoustics was selected among three firms.

<< Overview of the Central Conservatory of Music Hall Project >>

The conservatory's new hall will seat an audience of 800 to 1,200 persons for recital, chamber music and orchestra concerts. Use of the hall for opera performances is also part of the hall's programming. To obtain sufficient ceiling height above the stage when the hall is configured for concerts, the opera configuration's orchestra pit will be able to be raised to the stage level and used as a portion of the stage. A similar design is adopted for 3 other projects: Tokyo Bunka Kaikan's large hall; Conservatorium Theatre at Griffith University's Queensland Conservatorium, in Australia that we completed in 1996; and for the Richard B. Fisher Center for the Performing Arts that opened in April, 2003, in Annandale-on-Hudson, New York.

Currently, we are finalizing the details for the project's room acoustical design. Construction of the structural concrete walls of the building is also nearly complete. The planned opening of the hall is by the end of 2015.

Acoustical Design Legacies and Lessons of Older and Bygone Halls - Part 7
-Diffusion in Sound Fields and Hedgehog Visualizations-

By Dr. Minoru Nagata, Founder of Nagata Acoustics

When sound is generated inside a room, the sound reflects off the ceiling, walls and floor, creating a complex sound field. We use the term "perfectly diffuse sound field" to describe a condition of uniform sound intensity and direction of sound incidence throughout a room. Postulating this condition has been relied on to develop sound reverberation theory.

At a time when the prevailing goal of most concert hall acoustical designs focused on abundant sound reverberations, a number of design projects adopted the perfectly diffuse sound field as their ideal goal and focused solely on implementing ceilings and walls that would scatter the incident sound throughout the hall. Nowadays, however, the key concern for room acoustical design has become achieving lateral sound reflections.

Typical hall designs have elements on the ceiling and walls intended to scatter the incident sound. In particular, the design and incorporation of such elements on a hall's side walls can become an area of intense negotiation-if not contention-between the acoustical consultant and the project architect.

<< R. Thiele's Pioneering Research to Calculate and Visualize Sound Field Diffusion >>

R. Thiele's Igel
Photo 1: R. Thiele's Igel ("hedgehog")

In this article I wish to introduce readers to the Igel ("hedgehog") visualization of the incident sound distribution at a single point in a sound field. The German acoustician R. Thiele presented a 3D model (shown in Photo 1), known as the Igel or hedgehog, in an article1) published in 1953. Importantly, in the same article, he introduced the use of the index "d " and a method for calculating a diffuseness of a sound field. (See equations (1) and (2) below.) As far as I know, at the time Thiele published his research, he was the sole researcher investigating on the degree of diffuseness in a sound field.

The 1953 article provides detailed steps for building a 3D hedgehog model. First, set up an audio point source on the hall's stage, place narrow directional microphones at the audio receiving points and record the sound pressure levels. Next, calculate the sound intensity and, based on the calculated results, make rods of proportional lengths for the directions. Finally, insert the rods into a metal hemispherical base so the lengths pointing in each of the directions form a visual representation of the intensity of the incident sounds in the hall.

Two examples of hedgehog visualization and their respective directional distribution values
Fig 1: Examples of hedgehog visualization and
their respective d values for different diffuser
conditions in a reverberation chamber2)

Using the hedgehog visualization, Thiele was able to show that the value "d " indicates the level of the sound field's diffuseness. In a perfectly diffuse sound field, the directional diffusivity "d " equals 1. In a free field condition, "d " equals 0 (zero). For sound fields in between these two extremes, the "d " value is between 0 and 1.

Equation (1)


Equation (2)


In equation (2), Ei is the intensity of the incident sound in the i direction and n is the number of directions measured. In equation (1), m0 is the value of m in a free field.

<< Practical Application of the Hedgehog Visualization >>

I had the opportunity to make practical use of a hedgehog measuring device at a radio studio during the era of the first NHK Hall. In a corner of the JOAK Tokyo Broadcasting Building s, a 5,000 m3 studio for classical music (Studio CR507) was built. Including its stage area, the studio had about two-thirds' the floor space of the old NHK Hall (spatial volume: 8,700 m3). Unfortunately, the studio's acoustics became the source of complaints by the sound engineers who used it. Specifically, it was said that the sound "moves around" and that the "acoustics has bad separation of sounds".

The tool that we used to determine the root cause of the studio's problem was a device we had just made at the Testing Unit of NHK Research Laboratories. The device, which we called the hedgehog device, was designed to take measurements in a room and produce three-dimensional hedgehog visualizations. With the collaboration of my two colleagues Teruji Yamamoto and Hisashi Wakuri, we published the results of our testing in a report entitled "A Comparison of the Acoustical Characteristics of Two Radio Studios" (in the July 25, 1966 reference materials of the Architectural Acoustics study report of the NHK Research Laboratories' Acoustics Research Department).

In addition, through the kind help of D. W. Kuhl of the West German Radio Research Laboratory, the report was published in German in a special issue of that organization's journal3) and research funding was provided to build and perform tests with hedgehog devices made using the NHK Labs' design, including the audio source point mechanism (a paper origami popper that generates pulsive sound when briskly waved) and a revolving microphone mechanism. The device was built but later dismantled and, sadly, no longer exists.

<< After Analog Hedgehog Devices Came the Digital Revolution >>

The use of the hedgehog device and hedgehog visualizations that I described above used analog methods to represent the sound field characteristics of halls and studios. In this area of research, the hedgehog device may have been one of the last advances using analog technology. Widespread use of digital methods to analyze sound fields and develop acoustical designs comes in a little later on.

On the topic of the proliferation of digital technologies, I will note here that the first time I heard about digital technology was from NHK Labs' Kenji Hayashi, a then more junior engineer than me who worked in the Recording Research Unit. In 1970, he used a video recording device of the time to successfully digitally record a video. Thereafter, when Dr. Heitaro Nakajima had changed employment from NHK Labs to Sony Corporation, Dr. Nakajima and his team collaborated with Philips engineers to develop a complete system that resulted in the disappearance of LPs and proliferation of CDs. 30 years have already passed by since the appearance of audio CDs and about a half-century from the inception of NHK Research Laboratories' Acoustical Research Department. I continue to reflect on the advances we made, the technologies of today and what future research may achieve.

1) R.Thiele,"Richtungsverteilung und Zeitfolge der Schallrückwürfe in Raumen", Acustica, vol. 3, no. 2, 1953
2) M. Nagata, Shinban Kenchiku no Onkyosekkei ("Architectural Acoustics"), Chap. 5, Sec. 3, p. 111, 1991
3) M.Nagata, Rundfunktechnische Mitteilungen, vol. 13, p. 208, 1969

A Well-Attended Day of Lectures on "Recent Trends in Solid-Borne Noise Problems"

By Ryoichi Wada

On December 11, 2013, I attended a day of lectures sponsored by the Acoustical Materials Association of Japan on the topic of "Recent Trends in Solid-Borne Noise Problems". Examples of this problem include footsteps of neighbors and the noise of office building machinery heard in offices despite the machinery being located in a separate electrical or equipment room. In buildings that lack sufficient and appropriate measures to mitigate solid-borne noise, problems arise when the noise prevents workers from accomplishing their duties or affects the quality of residential life.

<< Overview of the Event >>

Among the day's attendees I saw many construction and real estate industry professionals. The lectures' five presenters were all extremely knowledgeable veterans of industry and academia with hands-on, practical experience. During the question and answer periods, one after another of the audience attendees avidly sought answers in a lively, participatory forum.

The lecturers addressed problems of solid-borne noise generated from sources both inside and outside of buildings. An example of a solid-borne noise source outside a building is a passing railroad train and an example of an indoor source of solid-borne noise is building machinery. Solid-borne noise can also often be caused by simple everyday activities such as walking across a room.

The situations and prevention strategies discussed in the lectures focused on practical acoustical engineering solutions available for businesses to adopt now. One lecture highlighted the many disputes that develop due to solid-borne noise complaints, and what society at large and the Acoustical Materials Association, in particular, should do in response.

<< Defining Solid-Borne Sound and Avoiding Mistakes during Construction>>

Solid-borne sound refers to sound that is not directly transmitted through the air, but instead, through the building's physical (solid) structure and then emitted into the air of a room where the sound can be detected and heard by the human ear. The lecturers gave examples of anti-vibration strategies implemented for solid-borne noise from railroads, building machinery and other sources and explained how to predict the solid-borne sound transmission.

In addition, the lecturers cautioned the audience about mistakes that can easily occur on construction jobs during the implementation of anti-vibration strategies. The information imparted in these real-life examples and suggested prevention and mitigation strategies should be especially valuable to the audience attendees who work in construction.

<< Litigation Trends and the Need for Solid-Borne Noise Evaluation Standards >>

The lecture of Nihon University Department of Engineering Professor Katsuo Inoue covered the topics of evaluating solid-borne noise, noise-related standards and recent dispute and litigation trends regarding solid-borne noise problems in condominiums. For the latter topic, Prof. Inoue referenced statistics published by The Center for Housing Renovation and Dispute Settlement Support (CHORD). The data reveals that for disputes involving newly constructed condominiums, in cases where the parties sought professional advice, the overwhelming majority of complaints concerned unwanted noise, with the sound of footsteps in adjacent units being the most frequent cause of the noise-related disputes. Also, for disputes that escalated to formal litigation, the primary cause of the dispute was noise, with solid-borne noise being the primary cause of litigated noise problems. Citing the data about disputes and litigation, Prof. Inoue has been urging associations to take note of the voices of condominium buyers and owners as expressed in the many reported disputes and to produce and adopt evaluation standards.

Among the complaints filed by condominium owners, complaints of solid-borne noise from adjacent-unit footsteps far outnumber other causes of complaints and disputes, such as complaints due to cracking plaster or other interior issues. Anti-vibration technologies and strategies already exist for eliminating or mitigating noise from people walking in adjacent spaces, passing trains and nearby vehicular traffic. However, in the current real estate market, developers and builders typically prioritize just the two goals of minimizing costs and maximizing space. Focusing on these two priorities can and often does result in insufficient attention to implementing measures for solid-borne noise mitigation.

In order to realize appropriate acoustical environments in condominiums and other multi-unit dwellings, businesses and associations need to listen to the voices of condominium owners and tenants. Anti-noise strategies should be incorporated into building designs during the planning stage and their value should be recognized alongside cost and space requirements. The lectures I heard at this gathering strengthened my understanding of the importance of pursuing this goal.

The 2013 CHORD Report (based on data collected in 2012) is available in Japanese.

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

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Los Angeles, CA 90025, U.S.A.
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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 ]