Quietness, Comfortable Sound and Excellent Acoustics NAGATA ACOUSTICS

News 07-11 (No.239)

Issued : November 25, 2007

[ Japanese Version ]

China's New Shenzhen Concert Hall

by Dr. Keiji Oguchi

In China's Shenzhen City, where the city's status as a Special Economic Zone has been a catalyst of rapid and remarkable growth, the new Shenzhen Concert Hall complex opened on October 12, 2007. In 1979, then CCP Chairman Deng Xiaoping established Shenzhen City's status as one of China's first Special Economic Zones, a fitting selection given the city's proximity to Hong Kong. The year that the city became a Special Economic Zone, Shenzhen's population numbered 300,000. Now, 27 years later, the city is home to 12 million people, an indicator of how the mesmerizing speed of growth has transformed the city. Each time I visit the city, I see new skyscrapers added to the skyline.

Most international visitors to Shenzhen travel to the city via Hong Kong, taking the eastern rail route, the western ferry route or a bus route that uses a road in-between the railway and ferry options. Regardless of which means of transportation chosen, from Hong Kong, the trip lasts not more than an hour.

The new concert hall is located in Shenzhen City's central Futian District among other municipal, public-use buildings that include the city's new public library and a youth center. When traveling to Shenzhen via the bus route, visitors will find this area to be relatively close to the Huanggang border. The concert hall faces the new library, which opened one year ago. Together, the two buildings comprise the new Culture Center complex, creating a municipally-sponsored cultural hub and leisure destination for Shenzhen's burgeoning population. The concert hall completes the set of projects commissioned by the city's Cultural Affairs Bureau and realized over a period of 10 years under the direction of the city's Project Construction Headquarters Office.

An international competition selection process awarded the architectural firm of Arata Isozaki Atelier the honor of designing the library and concert hall buildings. Nagata Acoustics participated on the concert hall project as the Acoustical Consultant, providing a full range of acoustical design and acoustical construction management services.

<< Architectural Overview: Using Color to Balance the "Five Elements" >>

Exterior of Shenzhen Concert Hall
Exterior of Shenzhen Concert Hall

The Shenzhen Culture Center complex has a long, 300 m. (984 ft) footprint in the north-south direction. A boulevard runs east-west through the center of the site, bifurcating the complex into north and south halves. The concert hall occupies the northern half and the library the southern half of the location. The exterior of the complex incorporates the traditional Chinese concept of balancing the "Wuxing, five elements," by including yellow, red, blue, white and black in its color scheme.

Shenzhen Concert Hall's gold-colored entrance and the library's similar silver-colored entrance, as well as the red and white interior of the large Symphony Hall all exude the splendid colorings that are hallmarks of Chinese decor. My amateur photography would not do justice to the expansive scale of the new buildings, so I will refer the reader to the computer-graphics assisted movie on the Shenzhen Concert Hall website for a panoramic tour of the buildings' exteriors and surrounding environs.

<< Shenzhen Concert Hall's Symphony Hall >>

Shenzhen Concert Hall's Symphony Hall
Shenzhen Concert Hall's Symphony Hall

1/10 scale model of Symphony Hall
1/10 scale model of Symphony Hall

Shenzhen Concert Hall's Symphony Hall has a vineyard configuration that surrounds the stage and a seat count of 1,800. At the widest point of the audience seating, the room spans 45 m. (148 ft), 60m. (197 ft) long and has a ceiling height of 25 m. (82 ft). In keeping with the basic approach of the vineyard configuration, the hall has blocks of seating areas positioned step-by step in the hall. By taking a relatively large height among each seating block, we achieved a broad area of surfaces that generate effective sound reflections. When viewed from the stage, the blocks of seats give a very dynamic appearance to the hall. The Shenzhen Concert Hall's website describes the hall as having a "canyon terrace" in recognition of dramatic impression created by the rising blocks of audience seating.

Above the stage, at a height of 15 m. (49 ft), we suspended 30 mm. (1 in.) polycarbonate sound reflection panels. The undersides of these panels, which are the sides that face towards the audience, are finished with a layer of matte, metal mesh that renders the panels virtually invisible to the audience. In addition, we attached the stage lighting and sound system equipment to the frames of the sound reflection panels, further camouflaging their purpose as sound reflection panels.

We began the process of refining the basic configuration of Symphony Hall using computer simulations, then built a 1/10 scale model for additional detailed testing, after which we finalized the hall's acoustical room design. During the year 2000, we borrowed a room on the Shenzhen University campus, so that we could build the 1/10 model and do our scale-model testing. As I recall the administrative work done to obtain our visas and import permits for the equipments we needed for the model test, I realize that the various steps and pitfalls that caused us consternation at the time have now become nostalgic anecdotes about the project.

In the interior of Symphony Hall, all of the wall surfaces are sound reflecting, with the exception of the rear wall behind the audience at the very back of the hall. During the 1/10 model testing, we discovered that this section of wall would cause a long-path echo if finished with a sound-reflecting material. We specified concrete as the material for the hall's large ceiling, a decision driven by the acoustical need to obtain sufficient mass for this element of our design. On the ceiling's surface, we created a fine, three-dimensional pattern of protrusions and indentations for having a sound scattering effect at high frequency. For the walls surrounding the audience seating area, we created a surface that effectively promotes sound scattering by combining the use of light concrete panels with random-width pieces of timber milled to a triangle pole and placed horizontally along the concrete walls. On the stage, we initially proposed the use of a conifer wood for the stage floor and, eventually, decided to import Japanese "Hinoki" cypress for this purpose.

<< The Theater Studio Small Hall >>

Theater Studio
Theater Studio

Shenzhen Concert Hall's small hall, officially named the Theater Studio, has the same type of configuration as Akiyoshidai International Art Village Concert Hall, with a flat main floor and two levels of "Flying" configurable seating. The stage floor is comprised of 20 sections that can each be raised independently to create a multitude of stage configurations. Depending on the stage configuration, the Theater Studio accommodates between 400 and 580 audience seats.

During the design phase of the project, the planned intention for this space was a recital hall. During the construction phase of the project, the stage mechanisms, stage lighting and a sound system were added and "Theater Studio" became the official name given to the room. Because the basic shape of the room retains its original recital hall dimensions, including a ceiling 14 m. (50 ft) high and a rather long reverberation time characteristic, the Theater Studio may be used equally successfully for music recitals as for experimental theater performances.

<< Shenzhen Concert Hall's Inauguration >>

On October 12, 2007, I returned to Shenzhen for the hall's opening night, after what seemed like a long absence from the city. The internationally acclaimed pianist Lang Lang performed as concerto soloist, bringing world class virtuosity to this first gala event in the concert hall's history. We have not yet conducted the final acoustical measurements on the hall, but during the opening program's rehearsals I was able to sit in a number of different seats and confirm the sound's clarity as well as its richly balanced acoustics. Lang Lang told us that the hall makes him feel as if he is dancing in mid-air and that it reminds him of the Berlin Philharmonic Hall.

I hope to return to Shenzhen in the near future to enjoy other performances and complete the hall's acoustical measuring. When I have had that opportunity, I will share more about Shenzhen Concert Hall with our readers.

Sound Isolation Design - Part 4 of a Series:
- Placement studies for auditorium facilities

by Chiaki Ishiwata

Not long ago, I turned on the TV and, to my amazement, heard a popular talk show host talking about acoustics! On October 3, 2007, a Tokyo court handed down the decision to fine the father of a young child because of noise the child repeatedly generated by running and jumping in a Tokyo condominium. The noise level recorded in the unit below floor exceeded 50~65 dB. In addition, the presiding judge commented on the lack of sincerity expressed by the child's father. I think that the justice took this factor into consideration in making his decision on the case.

This is the fourth regular article in our series on sound isolation design. In past articles, we discussed the need to consider the anticipated loudness that will be generated and also the level of quietness required. With these two sets of data known, the next set of planning activities is to consider different floor-plan options along with the structural sound isolation strategies that would be required with each floor plan option. Thoughtful placement design can reduce the need to build sound isolating features into a building's structural design. In this article, I will provide an overview of the aspects of auditorium buildings' placement designs that ought to be considered for their impact on sound isolation needs. Readers may also wish to review the July 1998 and September 1998 issues of this newsletter, which provide additional information on this topic.

<< Site Placement and Sound Isolation Design >>

If the footprint of an auditorium project's site allows, the first placement decision to be made for sound isolation design reasons is to distance the building as much as possible from any nearby major traffic arteries, large-sized shopping malls and so on. Typically, a hall foyer and corridors wrap around the outside of a hall's audience seating area, providing a buffer between that part of the hall and the building exterior.

However, on the stage side of the hall, a large flytower wall often serves as the only separation between the hall interior and the building's exterior, and generally a large opening is cut in this wall to serve as the stage's delivery entrance. Surely, each project weighs the benefits of convenient delivery functionality compared to sound isolation objectives; in locations where the building exterior behind the rear of the stage faces onto a heavily traveled road, creating a direct delivery access from the stage to the road is best avoided.

Unlike motor vehicles, trains and underground subways run on metal wheels not cushioned by tires. As a result, rail transportation creates large amounts of vibrations that pose problems for halls. If a train or subway line runs within 50 m. (164 ft) of a planned hall, in most situations, the hall will require an anti-vibration strategy, such as use of a floating structure or an underground anti-vibration structural solution. When the auditorium's site is adjacent to a train or subway line, the first steps are to attempt placement of the building at a distance greater than 50 m. (164 ft) from the transit line and to conduct on-site vibration measurements to determine the level of anti-vibration design required.

When the project site is located in a residential neighborhood in proximity to private homes or multi-unit dwellings, the sound volumes that are expected to be generated in the hall need to be considered during the site placement planning. Again, the first design approach is to maximize the building's distance from the nearby dwellings. As an additional sound isolation measure, the designers may also decide not to place windows or exhaust ducts on a side of an auditorium building that is near residential housing.

<< Placement for Multiple Halls and Rehearsal Rooms >>

An example of a floor plan that places backstage area between a hall and a theater  Nagaoka Lyric Hall (by Toyo Ito & Associates, Architects)
An example of a floor plan that places backstage area
between a hall and a theater
Nagaoka Lyric Hall (by Toyo Ito & Associates, Architects)

When an auditorium building will house multiple performance halls or a hall and a rehearsal room, the most desirable design provides acoustical independence for each of the halls and rehearsal rooms, with a high level of sound isolation that enables simultaneous use of all of the facilities. If the rooms will be used for music genres and instruments that produce extremely loud and low-frequency sounds, such as rock music and Japanese taiko drums, then physical separation alone will not be a sufficient design strategy to fully isolate these kinds of sound, as mentioned before in part 2 of this series. However, if, for example, one space will be used for seminars and lectures, and the building's other hall will be used for performances by a mid-sized orchestra and for piano music, then by establishing a floor plan that separates these two spaces by a distance over 20 m (66 ft), the appropriate sound isolation performance levels about 80dB in mid-frequency range can be obtained without designing and installing special sound and vibration isolation structural elements.

One example of a sound-isolating floor plan design for a building with multiple performance spaces is to establish a center, core zone occupied by dressing rooms and administrative offices. Another approach puts the building's small practice rooms at the center of the building and provides sound-isolating structural designs for these smaller spaces, while these rooms also double as a kind of buffer zone that separates the large performance spaces from each other and enables physical distance to be used as a sound-isolation strategy for the larger spaces.

<< Placement of Mechanical and Electrical Rooms >>

The rooms where noise generating equipments are installed within auditorium buildings are HVAC (Heating, Ventilation and Air Conditioning) rooms and electrical equipment rooms, etc. These rooms can be sources of noise that require sound isolation strategies. In order to minimize the length of HVAC ducts, a hall layout design may place the HVAC room at the side of the hall. If the hall requires quietness of NC-25 or lower, then we design the space in-between the corridor or duct shaft and the hall to have at least two wall layers or slab layers. In addition, space needs to be allotted to dissipate the noise produced by air moving in the HVAC duct between the HVAC room and the hall. If the HVAC room is located near the hall, a strategy may also be required to address vibration produced by the boiler, chiller and pump, as this vibration may transfer to the hall as solid-borne noise via the pipes.

HVAC, mechanical and electrical rooms typically produce large vibrations that require a vibration isolation strategy to address the transfer of these vibrations that occurs in the form of solid-borne noise. As a first sound and vibration isolation step to address the noise and vibration from these types of ancillary rooms, we recommend that these rooms not be placed directly horizontally adjacent to the hall and that at least one span of space be allowed between the hall and this kind of room. Additionally, our minimum specification for a room with HVAC equipment that produces vibrations would be a slab of at least 200 mm. (8 in.) thick, and each piece of equipment would need to be evaluated to determine the amount of vibrations it produces and an appropriate isolation strategy. The amount of vibrations produced is often related to overall structural design decisions, so the best time to begin the vibration mitigation and isolation planning is simultaneously with the start of the basic structural design work. As discussed in the June 2006 article on lavatory noise, to mitigate solid borne noise concerns, the placement of a corridor or other space between a hall and noisy equipment rooms is a beneficial design approach.

<< Placement of Stage Equipment Rooms >>

Auditorium also needs to find a place for the rooms that house equipment and machinery unique to buildings with stage facilities. The stage equipment that needs to be housed in its own space may include batons for hanging equipment above the stage, mechanisms for raising and lowering stage floor risers, electrical equipment rooms for pulleys and other mechanisms to raise and lower stage curtains, backdrops and batons, rooms for controlling stage lighting, sound system rooms and rooms for amplifiers. Concert halls rarely have the need to move batons or stage floor risers during actual performances, but opera houses and theaters use these apparatus as an integral part of the performances and, therefore, mechanical and electrical noise mitigation strategies are essential in these performance environments. Since the noise generated by these apparatus is not very loud, our approach is the same as for the rooms we design to house amplifiers. Basically, we surround the room with sound isolation drywall materials built on top of a concrete slab surface. The resulting enclosed space sufficiently isolates the stage equipments' noise from the audience. With regard to the room used to house the sound system amplifiers, because the amplifiers generate a large amount of heat, these rooms require cooling and ventilation equipment. To prevent this equipment's noise from transferring to the performance space, we make sure to obtain a path for the cooling and ventilation ducts that does not pass through the hall's space.

The electrical lines in the dimmer room create a humming sound that should be addressed as part of the sound isolation design. The first step in tackling this concern is to be sure to place a concrete wall between the hall and the dimmer room. In consideration of the possibility of solid borne noise transfer, the specification of this concrete slab should be at least 200 mm (8 in.) thick, and the room must not be piled up on auditorium. Also, if the electrical equipment room and the dimmer room are placed in far separate locations, and the dimmer room is set up with a transformer, the transformer will produce large amounts of vibration, with the result that the dimmer room will need to have a floating structure vibration isolation strategy. An additional consideration for the dimmer room is the placement of separate routes for the high voltage and low voltage electrical wires.

<< Placement of Elevators and Escalators >>

In keeping with the goal of barrier free auditoriums, elevators and escalators have become essential auditorium equipment. The operation of these apparatus generates vibration, and the flow of that vibration as solid borne sound must be considered when deciding on the placement of a building's elevators and escalators.

The fundamental rule to follow is that these apparatus not be directly supported by the walls that immediately surround the hall or by the slab on which the hall sits. Also, in general, if an elevator or escalator needs to be placed within a one-span distance of the hall, then any anti-vibration strategy should be installed specifically to mitigate the vibration from that apparatus.

<< Communicating with Auditorium Administrators about Sound Isolation Design >>

Ideally, the physical design of a new facility and the operational policies and procedures for the building's use both should be developed during the project's planning phase. The site placement and floor plan decisions, as well as the decision to implement structural sound isolation strategies are all key outputs of a auditorium's sound isolation design process. During the design period, the acoustical consultant has an obligation to share the content of the sound isolation design plans with the client and to collaborate with the client in aligning the client's operational plans and the sound isolation design plans. The alignment of these plans should be included among the criteria for completion of the design phase of the project.

In actual practice, project site and cost constraints combine with musical needs, such as the extremely loud sounds of Japanese taiko drums, to create situations that cannot be solved by the auditorium's physical design alone, no matter how much thought is given to the site or floor layout, or even to structural sound isolation strategies. Whether a auditorium's policies and rules are few or many, every facility needs an operational plan for how the facility will be used.

At the beginning of this article, I wrote about a court verdict related to a noise problem. While the specifics of that verdict do not have application to the main topics of this article, the concept that we must all be considerate of others when using a space is a lesson that holds for every environment. In concert halls, as elsewhere, let us enjoy ourselves and, at the same time, respond with our best human qualities in using these spaces together.

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

(US Office)
2130 Sawtelle Blvd., Suite 307A,
Los Angeles, CA 90025, U.S.A.
Telephone: (310) 231-7818
Fax: (310) 231-7816

E-mail: info@nagata.co.jp

[ Japanese Version ]