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

Nagata Acoustics News 06-08 (No.224)
Issued :August 25, 2006

Iwate Prefecture's Multifunctional Cultural and Activities Center -- "Aiina"

by Satoru Ikeda

Facade of Aiina
To the west of the Japan Railroad Morioka Station, Iwate Mountain rises impressively in the distance. In September 2005, the neighborhood in the vicinity of the station's west entrance welcomed a new, man-made treat for the eyes with the completion of the Iwate Prefectural Multifunctional Cultural and Activities Center, named Aiina Center. More recently, on May 8, 2006, the facility's Morioka Driving License Center, Iwate Passport Office and Iwate Prefectural Library together held a grand opening event to celebrate their move into the building.

The Iwate Prefectural Government constructed Aiina Center as a redevelopment project at the west entrance of Morioka Station to give the citizens of this prefecture a tangible boost into the 21st century. The center provides a central location for community interaction, accessing of public administrative services and opportunities to learn, participate in activities, be entertained, and exchange ideas.

<< Overview of Aiina Center >>

Aiina Center occupies a site along the traffic plaza of Morioka Station's west entrance and is adjacent to the Marios office tower, a 20-story hi-rise that houses Morioka City Cultural Hall, leased office space, conference rooms, shops and restaurants. Aiina Center has nine floors above ground and one basement level. The building's unique architectural design includes exterior, V-shaped columns supporting a dramatically sloping, concave-arc shape covered with a glass, double-walled skin fitted with large-sized louvers that promote efficient energy use. Together with the Marios Building funded by Morioka City, Aiina Center serves as a symbol of this neighborhood's revitalization.

The planners of Aiina Center expect this facility to serve as the prefectural cornerstone and leading presence for this section of Morioka City. In keeping with this role, Aiina Center houses a truly diverse range of bureaus and administrative offices in addition to the new Aiina Hall. The Morioka Driving License Center occupies the first floor. The second floor has the Iwate Passport Office and the Iwate Prefectural Housing Plaza. On the third and fourth floors are the Iwate Prefectural Library and the Iwate Prefectural Center for the Visually and Hearing Impaired. The fifth floor houses the International Exchange Center and the Environmental Studies Center. The sixth floor has the NPO Activity Center, Youth Activity Center, Equal Opportunities Center for Women and Men, the Senior Citizens' Activity Plaza and the Child Rearing Support Center, and on the seventh floor the Iwate Prefectural University Aiina Campus holds classes and has administrative offices. In addition to this long list of occupants, Aiina Center also offers airy indoor plazas for the general public and rentable galleries, the multifunctional Aiina Hall, Japanese-style rooms and conference facilities. The many activities, learning opportunities, information sharing, administrative and welfare services, and venues for cultural and inter-group activities make Aiina Center and Marios Building a "one-stop-shop" destination for residents and other people who come to this part of Morioka City.

The Aiina Center project's unique architectural design is the result of teamwork by a consortium of companies that included Nihon Sekkei, K. Sone & Environmental Design Associates and Kuji Sekkei. Kuji Sekkei is based in Iwate Prefecture and the other two firms practice nationwide in Japan.

<< Highlights of the Project Programming for the Center >>

The Aiina Center's desirable location, with its convenient proximity to public transportation, drew many ideas for the potential use of the site, and resulted in the center project having numerous stakeholders with a diversity of requirements. The architectural designers used a conceptual framework that divides the building into three zones dedicated respectively to Information, Activities and Learning. The architects aimed for each zone to be readily identifiable and for the whole structure to present an atmosphere of vitality, activity and human interaction.

At the center of the building, an escalator and glass-walled elevator move between floors creating a vertical axis through a large atrium. The Information Zone begins on Aiina Center's lower floors, where people seeking prefectural administrative services can access them readily, and continues up to the library. A large atrium dominates the center of the Activity Zone's floors, where the exchange and activity centers for every generation are located. On the top floors, the multifunctional hall provides space for speaking engagements and symposia that stimulate the intellect and foster a culture of learning among the prefecture's population, as well as conference and classroom space.

<< Aiina Hall's Layout and Interior Design >>

Interior of Aiina Hall
Aiina Hall spans a portion of Aiina Center's top seventh and eighth floors. The planning for this multifunctional hall focused primarily on a design for speaking engagements such as lectures, symposia, academic conferences, and exhibitions, as well as for international multilingual conferences. This flat-floored hall's footprint measures about 19 m. (62 ft) x 26 m. (85 ft), and the ceiling is 9 m. (30 ft) high. The front of the hall is equipped with a retracting projection screen, and a balcony at the rear of the hall has four simultaneous interpretation booths. To maximize the range of possible technical equipment set-ups when the hall is used with an entirely flat floor, seven ceiling catwalks have been installed at 3.5 m. (11 ft) intervals.

Front sections of audience floor can be lowered to create a stage. The hall's deployable seating includes an electrically operated stadium-style seating module of 275 seats and 232 stackable chairs, for maximum audience seating of 507. The ability to vary the height of portions of the hall's floor to create a stage or keep the floor entirely flat is particularly beneficial for events that target senior citizens and need to ensure the venue's accessibility.

The front wall of Aiina Hall is made of heavy cast steel with a finish inspired by the region's famous "Nambu Tetsu" cast ironware. The hall's sidewalls and rear wall are also finished with metal materials, the sidewalls being a combination of aluminum panel sections and aluminum louvers, and the rear wall being covered with perforated aluminum panel sections. The ceiling is a combination of aluminum panel sections and steel mesh, while the floor's material is Japanese white birch. In addition, upper portions of the left sidewall are made of transparent glass fitted with blinds that can be closed to shut out the external ambient light. The glass portion of the sidewall affords people in the hall the ability to view the mountains through the sub-foyer.

<< Acoustical Consulting Plan for Aiina Center >>

As the acoustical consultant on the Aiina Center project, Nagata Acoustics' responsibilities encompassed appropriate sound isolation between and among the multiple facilities and rooms housed under the same roof, equipment noise mitigation to prevent noise and vibration from the building's escalator and other machinery, and interior room acoustical design and sound system design of Aiina Hall. Our acoustical design plans included the following:

• Sound Isolation Strategy

Our planning for sound isolation in the center started with accepting two constraints: one, that the building has a structural steel framework; and, second, that the primary component of our interior wall specifications be some kind of drywall or other board materials. We considered the layout, location and purpose of the center's different rooms with the aim of achieving sound isolation ratings of D-50-55 between rooms. Given the needs of the occupants and the project's constraints, we implemented a double-wall construction that included placing a double-layer of 21 mm.(0.8 in.) gypsum board on each side of independent studs and uninterruptedly and completely filling the space between the boards with glass wool.

• Strategies for Loud-volume Sound

For the video studio and recording production studio in the Center for the Visually and Hearing Impaired in the fourth floor, as well as for the rental studios and practice rooms on the sixth floor, the seventh floor Aiina Hall and Aiina Hall's rehearsal room, the project's programming anticipated that very loud-volume sound will be produced in these spaces, or that the recording work and audience appreciation of events will sometimes require a high degree of silence. Therefore, in these rooms, we adopted sound and vibration isolating structure with two types of floating floors. One is with glass wool inserted as a sub-stratum and the other is with anti-vibration elastic materials installed using a dry process. In the fourth floor video studio, where bodysonic floor with built-in loudspeakers are part of the interior equipment requirements, and for the sixth floor room intended to be used as a dance studio, we installed a floating floor constructed with wet-sprayed shotcrete.

• Acoustical Room Design of Aiina Hall

Our approach to room acoustical design for the multifunctional Aiina Hall began by taking into consideration the existence of a multipurpose hall and concert hall right next door. This fact led us to focus Aiina Hall's acoustical design on the amplification of human speech and sound reproduction in conjunction with audio-visual screenings. Accordingly, a basic objective of our design work was to create a space characterized by a short reverberation-time. To this end, we created sound absorbing surfaces by installing glass wool covered with glass cloth behind the aluminum louvers on portions of the sidewalls and perforated aluminum panels of the rear wall, achieving a sound absorptive coefficient of 0.30-0.35 degrees.

• Aiina Hall Sound System

We designed Aiina Hall's sound system so that it provides equally effective speech amplification when the hall is configured with tiered seating and when used as a flat-floored space, as well as to enable the system's use as a public address system throughout the hall. Specifically, we installed a combination of a proscenium center loudspeaker and side loudspeakers for tiered seating and ceiling loudspeakers for flat-floored space, and planned for supplementary portable loudspeakers to be used to augment the soundtracks of movies and to create other sound effects.

<< A Project Requiring Close Attention to Innumerable Details >>

The Aiina Center project included requirements to meet the needs of many occupants plus a multifunctional hall. The structural design's use of a steel frame, separate sets of requirements for sound isolation from each stakeholder group, the architect's use of a glass curtain wall and the inclusion of major building machinery such as an escalator, all contributed to making the acoustical consultant's work during the construction phase of this project both intensive and detailed. We confirmed that each location was built in accordance with the acoustical design specifications to achieve the stakeholders' desired acoustical performance results.

The Aiina Center project implemented some of the most advanced techniques and approaches for environmentally friendly construction and energy conservation. The architectural design maximizes accessibility for people of all ages and for many people with special needs and even the center's artwork displays the planners' proactive adoption of state-of-the-arts techniques and technologies. Nevertheless, even in this quintessentially 21st century facility, the "backstage" and "behind-the-scenes" personnel will surely need to exercise effective space and scheduling management to make optimal use of different rooms' sound isolation characteristics and satisfy the center's many diverse constituents.

You can find more information about Aiina Center at its website. The URL is http://www.aiina.jp/en/index.html.

Installed Sound Systems /
Part 2: Desirable Qualities of Sound Amplification Performance and the Important Role of Loudspeakers

by Masaya Uchida

In Part 1 of this series (see our December, 2005 "News & Opinions"j, I looked at typical complaints about the quality of sound systems amplification of human speech and the causes of the problems these complaints identify. In this article, I will review the functional aims of different categories of sound system equipment and the key role that loudspeakers play in determining the overall perceived quality of sound amplification systems.

<< Categories of Sound System Functionality >>

At the most general level, sound system equipment provides sound amplification, reproduction, recording and intercom functionalities. Within the category of sound amplification, two subcategories can be further delineated: Public address systems primarily amplify speech and sound reinforcement systems amplify vocal and instrumental music at popular music concerts. Both of these two subcategories' functionalities provide sound amplification to listeners and also, through the use of fold-back loudspeakers, create environments conducive to delivering speeches or performing live music. While the sound amplified via a hall's system to its lobbies and dressing rooms has sound source and listeners in different spaces, it is also an amplification sound system.

Sound reproduction spans many kinds of content, from background music to pre-recorded music, speech and other sounds used in classroom instruction, lectures and presentations, from instrumental content used as the accompaniment to ballet and other dance forms to myriad sound effects used to enhance theater and opera productions. Sound reproduction uses as its sound source pre-recorded content, typically stored on MDs (minidiscs) and CDs.

Sound recording functionality refers to capturing both human speech (from speeches delivered at conferences, lectures and other speaking engagements) and music performed at concerts. Today's high quality recording equipment can capture the experience of a concert hall's specific acoustics and the applause and calls of "Bravo!" of the audience, at the same time as it records the music created on stage.

Intercom sound system equipment aids the communication of operational and backstage personnel, especially during the real-time course of an event or performance.

The specific sound system functionalities required and their criticality differ depending on the purpose and characteristics of a room, hall or facility. Nevertheless, whether the venue is a hall, theater or other performing arts facility, or whether it is a multipurpose event space, social hall, house of worship, gym, school, lecture hall, hospital, train station or airport, wherever people gather in numbers, some level of sound system needs to be installed. The most fundamental aim of sound systems is to amplify human speech so that it is conveyed to the ears of listeners who are beyond the range that the unaided human voice can reach.

<< Desirable Sound Amplification Performance Qualities >>

User expectations for sound amplification equipment begin with the assumption that the system will amplify speech accurately and clearly. Additionally, the equipment should deliver a quality of sound appropriate to the facility and nature of the event or circumstances. Let us consider the characteristics of the human speech that serves as the basic input of sound amplification. If amplifying the sound of a speaking engagement, the system should deliver sound that makes the individual voice of the person speaking recognizable and the audience should be able to listen at length without the sound amplification equipment causing listeners to feel fatigued. In a house of worship, the sound amplification of a sermon should enable listeners to distinguish if the preacher's voice conveys sternness or compassion.

The ability of sound amplification equipment to preserve the expressive quality of the human voice is especially desirable in sound amplification equipment used in theaters and for vocal music performances. Actors and singers use their voices to convey emotions and nuances of meaning well beyond the words in their scripts and lyrics. Sound effects need to be accompanied by the appropriate sense of power and realism. The efforts of performers and directors to express their creative and artistic visions depend on the sound amplification system to accurately transmit to the audience their desired sound quality.

Finally, in train stations and airports, sound amplification systems must often be able to produce sound quality that can be heard despite the noisy ambient environment of these facilities.

These qualities of sound amplification performance consist of sound quality, sound volume, sound directionality and so on. Human hearing has the capacity to make many sensitive distinctions from the human voice it hears, even when it receives relatively limited input. For example, when we hear a voice through a telephone receiver, the sound uses a narrow band of frequencies, yet we can recognize individual voices and interpret the emotional state and health of the person speaking. It does not take an expert to know if amplified sound is easy to hear or unintelligible, or if it sounds artificial or natural. But these judgments are unclear and difficult to quantify because they are sensuous or subjective, so that it tends to be despised. In addition, for this need and for all of the sound amplification characteristics discussed, the key to successfully implementing an effective sound amplification system is the selection and the location of loudspeakers and microphones from among the numerous brands and models available. Unfortunately, few concerns are given about the factors that influence the qualities of amplified sounds.

<< The Role of Microphones and the Person Speaking >>

Microphones, which transform the air vibrations we know as sound into electrical signals, play a critical role in determining the quality of sound obtained from a sound amplification system. No matter how advanced and high quality the sound amplification equipment itself may be, if the source sound that is input to the system is poor, then the output will match the poor sound quality of the source. The sound quality input at the microphone is precisely the sound that the sound amplification system amplifies.

However, the brand and model, placement, and quantity of microphones used at a venue varies from production to production and changes based on the number of people speaking or performing. Also, the people speaking into the microphones have voices with a range of loudness and varying levels of skill using a microphone. Some people project their voices well into the microphone while others talk too fast or have other difficulties using the microphone. The microphone skills of the person speaking significantly influence the quality of amplified sound.

Adjusting the microphone and entire sound amplification system are left to the technician or person operating the sound system. Therefore, the installed loudspeakers must be able to adapt to some degree of uncertain and imperfect input conditions.

When preparing a venue's sound amplification system for a specific event, the technician or system operator needs to take into account numerous factors besides the microphone skills of the people who will speak. For example, attention must be given to the relative placement of the microphones to the loudspeakers, if they are in the same room, to prevent hearing the disturbing howling noise caused by feedback. The specific acoustical characteristics of the room influence sound amplification as do operational considerations of the sound amplification equipment. Achieving the best possible sound amplification from a system can truly be a daunting task for non-professionals. Since only major halls and theaters have professional sound technicians, most sound amplification systems must be able to perform well without the supervision or intervention of a sound technician. These constraints all point us back to the critical importance of the system's loudspeakers, which the acoustical consultant designing a system can specify and install, ensuring that even an unattended sound amplification system performs effectively.

<< The Importance of the Loudspeakers to Overall Success >>

To achieve natural-sounding, superior quality sound amplification, the most important equipment on which to focus are the loudspeakers. The performance characteristics and installation conditions of the loudspeakers, which are the part of the system that transforms electrical signals back into the sound the audience hears, greatly influence how listeners experience a sound amplification system. At theaters equipped with a full complement of production equipment and personnel to manage production set-ups, each new production includes outfitting the theater with the appropriate number of loudspeakers, placed and angled according to a plan that will showcase the performance optimally. But many facilities use loudspeakers that were fixed in place as part of the sound system's installation. The essential concern when determining placement of fixed loudspeakers is achieving rich sound quality, equal sound level distribution and sound's directionality for the entire audience.

Indoors, the sound waves emitted by loudspeakers travel in direct paths both to listeners and to the room's walls and ceiling. When the loudspeaker-generated sound reaches the walls and ceiling, it unavoidably creates sound reflections back into the room. (Of course, sound absorbing walls and ceiling treatments can affect the amount of sound reflections.) In order to minimize the affects of these sound reflections, when an acoustical consultant designs a sound amplification system, the design must ensure that the sound volume of the direct sound that reaches the audience from the loudspeakers exceeds the sound volume of the reflections. Because loudspeakers can only deliver the optimal balance of low and high frequency sound to limited coverage areas, it is essential to angle the placement of the loudspeakers so that the entire audience is included in the loudspeakers' coverage areas. This means that, from the perspective of a person looking at the loudspeaker from an audience seat, the front of the loudspeaker is visible within a certain specifiable angle.

Architectural designers of room interiors find loudspeakers challenging. Loudspeakers typically look like big black boxes. They are heavy in weight and, unlike lighting fixtures, cannot be designed into artistic objects. All of these characteristics make loudspeakers problematic for architects to include in their designs. Understandably, the architect prioritizes the visual aesthetics of the interior design and may suggest that the acoustics will not be impacted if the design partially hides the loudspeakers from the audience's view. However, such a configuration means that the sound reaching the audience seating arrives after the sound waves wrap around the obstacles that hide the loudspeakers from view, so that the sound the audience hears becomes a combination of the sound frequency bands long enough to travel around the obstacles plus the sound reflections from the walls and ceiling. For sure, the quality of the sound the audience hears suffers.

Since sound, unlike light, is not visible to the human eye, we do not have an intuitive understanding of what happens when sound encounters an obstacle in its path. However, similar to the phenomena we experience with light, when sound encounters an obstacle, shadows are produced and the front of the sound wave scatters and becomes distorted. When we can hear sound, but it is indistinct and the content unintelligible, the problem can usually be traced to the conditions caused by the sound waves having encountered one or more obstacles.

The priorities that determine the most desirable placement for loudspeakers and the priorities that drive the interior design of a space naturally differ. Resolving issues resulting from these differing priorities requires the close cooperation and mutual understanding of the architect and the acoustical consultant designing the sound system.

In many cases, sound system's problems rise up after completion of the construction and operation started. Interestingly enough, when the problem occurs in a facility that is used by random individuals, the problem rarely escalates to a complaint and the facility accepts the imperfect system functionality. One of the causes of these problems is that the facility owners and architects are lack of the concern about qualities of the amplified sound in early design phase.

I expect the importance of the loudspeakers for the performance quality of sound system to be recognized better.

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Nagata Acoustics News 06-08 (No.224)
Issued : August 25, 2006

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