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Essert engaged subconsultants and colleagues in Toronto to help with fine-tuning the building's acoustics. John O'Keefe and his company Aerocoustics and Phil Giddings of Engineering Harmonics (audio and video systems design) provided a local presence. The team was also supported by Wilson Ihrig and Associates, Inc. of Oakland, California, specialists in vibration isolation.

R. Fraser Elliott Hall was created specifically for the acoustics and sight lines required for opera and ballet and for the intimacy characteristic of the world's great opera houses. No seat in the hall is compromised, regardless of ticket price, with 73 percent of all seats within a 100-foot (30-meter) cylinder of center stage. The lack of a frame around the proscenium arch means there is no interceding element between patron and performer, giving the audience a greater sense of connection to the stage.

Shaping the Shell

Essert says the classic horseshoe shape of the hall — four balconies stacked up so the audience is on five levels including the orchestra level — not only brings the audience close to the performance but also aids acoustics. "The stacked-up balconies act like a wall, with hard surfaces like the railing alternating with soft surfaces like the people in the seats," he says.

Essert adds: "The layers support the voices on the stage and control the orchestra a bit. The effect doesn't work if there are fewer balconies or a lot of space between the layers." The curved balconies gather sound while the hard/ soft contrast between railing and people scatters the sound, making a more balanced effect overall.

A.J. "Jack" Diamond, principal of Diamond and Schmitt Architects Inc., the building's designer, notes that seats in the corners of the hall traditionally have the worst sightlines. In this case, however, the floor sweeps up slightly so it is higher at the sides than in the middle of the row, thereby eliminating the problem. Similarly, the ceiling sides sweep up to throw sound back to the seats at the outer edges of the room.

Enclosed by a giant but gentle basket-weave plaster shell that is slightly toothed in texture, the shell serves two purposes: acoustic — sound reflection and diffusion — and visual — providing a human scale to the chamber.

Ceilings, too, are used for interior design and functional purposes. Made up of a series of layered plaster "clouds," these surfaces provide good reflection to reinforce the sound density. The interstitial spaces between the layers provide a variety of concealed stage-lighting positions, including a follow-spot booth.

Audience Absorption

It may seem odd that such an elegant performance hall lacks carpeted floors, but Essert feels carpeting would negatively affect the room's acoustic quality. "Carpet would soak up too much sound," he says. "The 2,000 audience members do a good enough job."

Instead, the floor is one of the solid surfaces, together with the ceiling, walls, and balcony fronts, that reflect sound during performances. The orchestra pit is constructed of just enough layers of wood to support the load of the orchestra — 13 feet (4 meters) above the concrete floor. In the audience areas, wood was laid directly onto the concrete, and the chairs are screwed right onto that.

Essert notes that it is possible to adjust the acoustics of the room, ensuring the best sound for any given performance. For example, heavy but low-cost fabric banners can be scrolled down the walls to catch some of the sound energy that would normally bounce around the walls. They make the space more sympathetic to the lighter voices common in musical comedy.

Isolation Imperative

Nearly as important as the quality of sound is the reduction of noise penetration. To reduce the noise in the performance venues, the auditorium, stage, and rehearsal hall were designed to be an entirely separate and isolated structure within the building. Encased in a double layer of concrete and sitting on nearly 500 rubber pads, the main hall carries the coveted N-1 isolation rating.

"The rubber pads isolate the central house so that it doesn't vibrate," says Diamond. "All ducting and piping coming into the house does the same thing. The result is this is likely the quietest opera house in the world."

Darius Zaccak, construction manager for general contractor PCL Constructors Canada Inc., says acoustical concerns created some interesting challenges for the construction team. For one thing, the below-grade garage had to be isolated from the above-ground structure using rubber pads. But there were problems with the installation of the pads during mock-up, requiring adjustments in construction processes.

Zaccak explains: "The acoustical joint — the place where the quiet part of the building meets the nonquiet part — has lots of services going across it. We shone a light between the two parts to make sure not even a nail was touching the two."

Services were installed using flexible connections to further ensure there was no sound transmission. And that's not all. "All ductwork was internally lined to dampen any sound," says Zaccak. "It's not easy to work with the liner on site because it can get wet, damaged, and dusty while the liner is still in pieces. So this was a more delicate and careful installation than most."

Zaccak insists the Four Seasons Centre for the Performing Arts is the most interesting building he's worked on in his 25 years in the construction business. "The complexity of the project was really interesting," he says. "Nothing was repeated, as it is in most buildings. We only had one chance to get things right."

Judging by the audience and performer response during the three test concerts prior to the official opening in June 2006, the opera house is ready to sing.

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Janet Collins is a freelance writer and editor based in British Columbia. She has written for Canadian Architect, Canadian Interiors, Canadian Facility Management & Design, and many other publications.

Jessica Muirhead, soprano, during a test of the acoustics. Photo: Michael Cooper Four Seasons auditorium ceiling. Photo: PCL Constructors Canada Inc. Section through auditorium, looking north. Image: Diamond and Schmitt Architects Inc. Extra Large Image Computed visualization of sound leaving the stage (at right), moving toward the audience. Image: Robert Essert/ Sound Space Design Sound reflecting from the various ceiling planes. Image: Robert Essert/ Sound Space Design Visualization of sound arriving at the audience. Image: Robert Essert/ Sound Space Design Acoustic pads. Photo: Claudine Domingue Back stage. Photo: Tim Griffith Photographer   Click on thumbnail images to view full-size pictures.