Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS


News 09-03 (No.255)

Issued : March 25, 2009

[ Japanese Version ]

Copenhagen's New Concert Hall Opens

by Dr. Yasuhisa Toyota

Denmark's Copenhagen ushered in the opening of a new concert hall on January 17, 2009 with a gala inauguration concert. The hall is part of the new headquarters of the Danish Broadcasting Corporation (Danish Radio) and was built in conjunction with the larger project's goal to house all Danish Radio offices and studios in a single location. Like Denmark, Japan also has a national broadcasting corporation, "NHK," and Tokyo has an NHK Hall. But while Japan's NHK hall is built as a multipurpose facility, Copenhagen's new Danish Radio Hall has the distinction of being designed specifically as a concert hall.

Danish Radio Concert Hall will be the home base of the Danish National Symphony Orchestra, which is closely affiliated with the broadcast network. The opening of Danish Radio Concert Hall marks Nagata Acoustics' completion of our first hall project in Western Europe.

<< The Project Architect and Acoustical Consultant Team >>

The new hall's conceptual planning began with the architectural design competition held in 2001 -2002. In 2001, the Danish Radio committee responsible for key decisions about the new hall traveled worldwide to experience other concert halls and prepare themselves for selecting the concert hall's architect. Then, in the autumn of 2001, the committee held a design competition, completing the selection process in early 2002 when it named the French firm of Ateliers Jean Nouvel as the project architect.

During this early planning phase, the committee also decided how to select the project's acoustical consultant and how to involve or associate this selection with the selection of the project architect. Throughout the world, each time the planning of a major concert hall begins, the decision makers typically reconsider the various approaches to selecting and forming the architect and acoustical consultant team. I wrote about the process adopted for Danish Radio Concert Hall in the April 2002 issue of this newsletter. A key aspect of the Danish Radio Concert Hall selection process was to have each short-listed architect select a short-listed acoustical consultant and, together, to have the architect and acoustical consultant jointly prepare and submit a proposal to the design competition. By the way, when I wrote about the design competition in 2002, I mentioned a target completion date of 2006. The actual completion date was two years later, in the autumn of 2008.

<< Danish Radio Concert Hall's Unique Architectural Design >>

Exterior
Exterior

Architect Jean Nouvel's design for Danish Radio Concert Hall has a notably unique exterior and interior. The exterior is enveloped in a thin blue fabric skin that functions as a projection screen. During the daytime, the building has a somewhat unusual appearance and almost resembles a structure still under construction that has been temporarily wrapped in cloth. When the dark hours of nighttime arrive, which happens before concerts begin, strong projectors installed outside the building send real and abstract images onto the building's skin, creating the illusion of fascinating landscapes and scenery.

The exterior design of this concert hall was surely conceived with the nighttime hours in mind. Fundamentally, a concert hall functions in the evening when most performances are held. If we combine this piece of information with the fact that the prime concert season is the winter months when the Nordic countries especially experience long hours of darkness, we can understand how Jean Nouvel's inspired design truly hits the mark for this concert hall in the city of Copenhagen.

<< The Danish Radio Concert Hall Interior >>

Interior
Interior

The Danish Radio Concert Hall interior has audience seating for 1,800 persons arranged in a vineyard configuration. Even though the so-called "shoebox," rectangular hall configuration has a reputation for good acoustics, the Danish Radio decision makers specifically selected the vineyard configuration, prioritizing the enhanced sense of intimacy and sense of presence that this configuration creates both visually and acoustically. At Danish Radio Concert hall, the audience can see the faces of other audience members seated in other seating blocks that rise above the stage on all sides.

The design of the hall interior took as its starting point the vineyard configuration of Berlin Philharmonic Hall and evolved to have a unique appearance. An abundant use of wood covers the sidewalls around the blocks of audience seating and the hall ceiling, and the sidewalls form beautifully flowing concave and convex curves. Overall, the interior color scheme uses light, reddish tones, creating a warm and welcoming feeling in the hall.

<< Timing of the Project's Completion and Opening Night >>

This project encountered delays and completed just before the January 2009 date of the gala opening. Orchestras and other performers need time to acclimate themselves to the acoustics of a new hall. From the date of the completion of construction until the opening date of a hall, at least three months of preparation time are required, and from the acoustical consultant's standpoint, the longer the period for fine tuning the hall the better.

Prior to the opening of Danish Radio Concert Hall, the orchestra had almost no time to rehearse in the hall. However, the Danish National Symphony Orchestra admirably adapted extremely quickly to its new home and I can gladly report that they performed the opening gala with barely a hint of being in a new environment.

<< The Opening Gala and Highlights of the Opening Season >>

Below is the list of 10 composers represented in Danish Radio Concert Hall's gala opening concert program:

(1)Andy Pape (1955- , Denmark)
(2)C.F.E. Hornemann (1840-1906, Denmark)
(3)Henri Tomasi (1901-1971, France)
(4)Ambroise Thomas (1811-1896, France)
(5)Camille Saint-Saens (1835-1924, France)
(6)Rued Langgaard (1893-1952, Denmark)
(7)Charles-Marie Widor (1844-1937, France)
(8)Carl Nielsen (1865-1931, Denmark)
(9)Jules Massenet (1842-1912, France)
(10)Maurice Ravel (1875-1937, France)

As the reader can see, the program featured the works of four Danish and six French composers. With the two exceptions of Saint-Saens' "The Swan" and Ravel's "Bolero," the entire program was filled with minor compositions that I, for one, was hearing for the first time. The program was recondite fare for a gala opening concert and the audience became energized by the "Bolero" finale. The Danish National Symphony Orchestra's first season calendar included large-scale works such as Mahler's Symphony No. 2 ("Resurrection"), Beethoven's Symphony No. 9 ("Chorale"), and Stravinsky's big three ballets, any of which would have been appropriate for an inaugural concert, the gala opening seemed even more somber by comparison.

Of the major works on this season's calendar, I had the opportunity to attend a performance of Mahler's "Resurrection." When I listened to the alto softly begin to sing the fourth movement and, later, in the fifth movement, when the chorus began to sing, the acoustics so moved me that I felt my skin tingle with goose bumps as I experienced these tone fill the air. This was when I knew for sure that the Danish Radio Concert Hall project was a success.

Due to the project's construction delays, our final acoustical measuring in the completed hall was moved to after the hall's opening and is still a pending activity. We expect to complete this task soon and obtain quantitative physical acoustics data. When we have the measurements, I look forward to sharing them with our newsletter readers.

For photos and other information, visit http://www.dr.dk/Koncerthuset/inenglish/koncerthuset_1.htm



Installed Sound Systems Series, Part 5: Preventing Noise Infiltration in Hall Sound Systems

by Masaya Uchida

Starting about 10 years ago, the problem of noise that infiltrated to sound system from other equipments became a topic of frequent serious discussion. Typical examples of sound system-related noise problems include noise that occurs irregularly and unpredictably during concerts, noise that can be heard in concert recordings, noise that infiltrates an intercom system and, more rarely, noise that causes projected video images to blur or display striped patterns during screenings. Noise problems related to a hall's sound system can become major operational impediments and limit a hall's use.

Noise generating sources increased as the use of inverter devices that vary electrical frequencies in order to control the cycle of motors became prevalent and hall facilities became both more multifunctional and more integrated. The same period saw advances in the signal-to-noise ratio (S/N or SNR) of audio devices and improved quietness of HVAC systems. Together, these trends resulted in noise mitigation becoming pertinent to sound system design.

In the below paragraphs, I will suggest some of the noise prevention and mitigation measures Nagata Acoustics implements based on our hall project experience.

<< Sources that Generate Sound System Noise and Infiltration Routes >>

Sound system devices and, in particular microphone circuits use weak voltage, making it easy for them to be affected by noise from other equipment. Certainly, sound system devices and sound system designs include ways to prevent noise infiltration, but the effectiveness of these prevention measures has limits. Therefore, it is also necessary to prevent noise generation and noise leakage at its sources.

Noise that infiltrates sound systems originates primarily from the high power-consumption equipment in a hall's machine rooms or stage-lighting dimmer rooms, as well as from the inverter devices that are often installed with HVAC systems and mechanisms that raise and lower stage floors, curtains and other apparatus, and related wiring. The ways that noise infiltrates a sound system can be broadly grouped into the following three categories.

  • Transmission: Noise can pass along a power source wire, grounding wire or signal wire and be transmitted to the sound system.
  • Emission: A device or wire that generates noise can emit unwanted electromagnetic waves into the air and the waves can infiltrate the sound system from the air.
  • Induction: The electromagnetic fields of nearby electrical wiring can induce a voltage on the sound system's wires.

Also, it is important to keep in mind that, unlike general electromagnetic compatibility efforts, sound system noise mitigation should be concerned with audible frequencies (20 Hz ~ 20 kHz).

<< Practical Prevention and Mitigation Methods >>

Below are summaries of some of the methods we use to prevent and mitigate noise infiltration into sound systems.

>> Pre-construction Planning

The simplest prevention method is to create distance between the noise generating sources and the sound system. As a fundamental principle, hall floor plans should avoid locating machine rooms, stage-lighting dimmer rooms and main power supply wiring in adjacent to the control room or wiring routes of sound system.

>> Electric Power Equipment

The sound system can be protected from noise come through power supply and grounding wires by installing a separate electric power transformer for the sound system. In implementing this strategy, it is important to also provide a separate safety ground for the transformer.

Fig.1  An example of the noise prevention in the electric power equipments.
Fig.1 An example of the noise prevention
in the electric power equipments.

On renovation and similar projects where use of a separate transformer is not possible, a noise-reduction transformer can be used, and the sound system load is attached to the noise-reduction transformer instead of to a separate transformer. However, this approach requires extra care in selecting a location for the noise-reduction transformer because these transformers have a tendency to generate a hum and heat.

In addition, to prevent the main power supply wiring that serves other systems from generating induced noise into the power supply wiring that serves sound system, we recommend using a separate piping for the sound system's power supply wiring. Fig. 1 shows an example of noise prevention in electric power supply equipments.

>> Signal Grounding

In addition to installing a separate safety ground for the sound system transformer, a separate signal ground (functional ground) should also be installed. The grounding electrode should be buried in a location near the sound system's control room and its wiring should connect to the control room via a conduit used solely for this purpose. All of the audio devices and electrical outlets for audio equipments should be distributed from this point to build a single-point star grounding arrangement. Also, the racks that hold the sound system equipments should be fixed to the structure with electrical insulation materials in order to ensure the separate signal grounding for sound system.

The recent trend in building construction is to integrate all grounding in the building structure so that the entire building is equally grounded through the adoption of an integrated grounding (also known as equipotential grounding). We can anticipate that this approach to grounding will become the main grounding method for future construction. The question of how sound system's grounding that we tried to separate from other equipment should be in this kind of environment has yet to be clearly answered. Currently, when a hall structure has integrated grounding, we also specify the installation of separate grounding as a precautionary measure. If a noise problem occurs due to the integrated grounding, the sound system can be switched to the separate grounding to resolve the problem.

>> Conduits and Wiring

Another fundamental principle is to create sufficient distance between other systems' major power lines and the sound system equipments and its circuits. To the maximum extent possible, we route the wiring of sound system separately from those of the stage-lighting system and power distribution system, dividing the wiring along routes that run at stage left and stage right of the hall. For portions of the distance where the conduits must follow the same route, we create as much distance as possible between the conduits and we avoid placing long sections of parallel conduit. Where conduit for one purpose must cross conduit for another purpose, we specify that the conduits must bisect each other at right angles to mitigate the possibility of generating induction-caused noise.

As a rule, we always use metal conduits and metal wiring ducts for all sound system wiring. When other systems' wiring is within certain proximity of the sound system circuits, we also use metal conduit for the other systems' wiring to shield the noise from them.

>> Stage Lighting Equipment

Because the dimmer equipment that controls stage lighting generates high levels of wave patterns known as triplen harmonics, it is important to use stranded wire to mitigate the possibility of noise from emissions caused by magnetic field compensation. We also follow the general of using metal conduit and metal wiring ducts for the stage lighting power source and load wiring. If stranded wire is not used, the magnetic fields are likely to cause the cable and wiring duct lids to vibrate, resulting in a noise problem.

Fig.2  An example of the noise from the wiring of stage-lighting system.
Fig.2 An example of the noise from the wiring
of stage-lighting system.

Given the noise-prone aspects of the stage lighting wiring, however, the very purpose of stage lighting means that there are many situations where wiring for stage lighting must be placed in the stage area. In these situations, extra care and caution must be exercised. Fig. 2 graphs an example of the effect of a lighting dimmer device's power supply wiring that was installed without shielding at 20 m above a stage. The graph shows the emission-generated noise that infiltrated the microphone cable of this stage.

>> Inverter Devices

Many devices now rely on the use of inverters and these inverters often generate noise at the same frequencies used by carrier waves. When multiple units of apparatus all generate noise at the same carrier frequency, the noise level adds up to an undesirable level. Therefore, it is important that the apparatus be equipped with inverters that allow adjustment of the carrier frequencies. Fig. 3 shows the noise frequencies generated by inverter devices used with supply air and return air fans before and after the inverter devices were adjusted to different carrier frequencies in order to reduce the noise level.

 Fig.3  An example of reduction of the noise from HVAC system's inverters. Carrier frequency of SA and RA fan: 15kHz
Carrier frequency of SA and RA fan: 15kHz
Fig.3  An example of reduction of the noise from HVAC system's inverters. Carrier frequency of SA and RA fan: 13kHz and 14KHz
Carrier frequency of SA and RA fan: 13kHz and 14KHz
Fig.3 An example of reduction of the noise from HVAC system's inverters.

Depending on the conditions, there may be a need to consider adding shielding and separate grounds among and between the inverter devices and wiring.

<< The Value of Noise Infiltration Prevention Measures >>

Noise infiltration in sound systems can arise from various conditions that cause the noise to be generated and transferred to the sound system. We do not have ways to reliably quantify this diversely caused phenomenon. Attempting to remedy a noise infiltration problem is both difficult and extremely costly. Therefore, it is extremely important to prioritize and give careful attention to noise infiltration prevention measures so that the problem does not occur.

Today and in the future, it is fair to say that no aspect of construction can consider itself as having zero impact on the possibility of sound system noise generation. Everyone involved in a project must be aware of the need to prevent noise and adopt designs and construction methods to prevent it from occurring.


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 307A
Los Angeles, CA 90025, U.S.A.
Tel: +1-310-231-7818, 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 ]