The Royal Conservatory of Music’s $110-million concert hall has the highest possible acoustic rating for a building. We talked to some of the designers to find out exactly what that means.
Thousands of commuters head north on the University line to St. George station every day, but it’s likely that few of them realize they’ve been travelling underneath one of the world’s most beautiful concert venues. Koerner Hall, which opened in the fall of 2009, is tucked in behind the glass façade of the Telus Centre for Performance and Learning, an annex of the Royal Conservatory of Music that’s located between the ROM and Varsity Stadium. The inside of the hall is stunning, crowned with undulating oak ribbons that appear to burst out of the top of the stage and into the ceiling. But Koerner Hall isn’t just visually striking. It’s aurally exquisite, earning the highest acoustic rating—an N1—a building can score.
Acoustics consultant Bob Essert helped design the space. As he explains, the N1 rating means that if you’re sitting in the audience, you won’t notice any audible background noise. “The auditorium itself is completely silent,” he says. It’s easy enough to make a pretty space, but constructing a perfect-sounding concert hall that’s situated on top of two sets of subway tracks and surrounded by a hockey arena, a football stadium, the traffic of Bloor Street, and a building full of instrumental rehearsals presents more of a challenge. And as we learned from Essert and Marianne McKenna, the lead architect on the project, which was created by the firm KPMB, every detail counts.
1. Lighting The noisy electronic ballasts, which regulate the electrical current for the hall’s lighting, are located in the lobby beyond the acoustic barrier.
2. Doors that release sound When the performance is too loud—as is the case during some amplified concerts, or when a large symphony performs—hidden panels in the walls open to allow noise to be “lost” backstage.
3. Seats The seats in the auditorium come in some 30 subtly different sizes to improve sightlines. They’re custom-made, with minimal upholstery and oak bottoms designed to reflect as much sound as possible.
4. Floors The subfloor of the auditorium sits on framing designed with air space throughout—this enhances the resonance of the low string instruments (cellos and basses).
5. Foundation Beneath the floor of Koerner Hall are hundreds of specially designed rubber pads. They provide a buffer against vibrations in the ground caused by the subway and by the ice refrigeration machines next door in Varsity Arena.
6. Best seats in the house “Every seat is good, but the top of the second balcony is really great,” says McKenna. “Sound hits [the wall] back there and comes back and wraps [around] you.”
7. The Baillie Veil Sound can travel up and through the Baillie Veil, which hangs anging 20 feet below the ceiling. The twisted and bowed oak strands that make up the canopy reflect a precise amount of sound back towards the stage so that musicians can hear themselves without having to rely on speakers or amplification.
8. Plaster walls Explains Essert, “The gray waves on the walls are solid plaster with a rough finish. They’re bonded to the solid masonry behind. The solidity supports the bass, the hardness supports the mid-range, the waves scatter the middle frequencies, and the roughness scatters the highest frequencies, so the sound is smooth and warm.”
9. Balcony fronts The boards on the front of the balcony have a slight convex curve, or crown, as well as shallow, almost microscopic grooves in their surfaces. Those grooves scatter higher frequencies, mitigating any harshness in the sound.
10. Acoustic isolation A small gap less than two centimetres wide, called an acoustic joint, surrounds the exterior of the room on all sides, shielding Koerner Hall from any vibrations from adjacent structures.
Air conditioning and ventilation: While residential ducts are inches wide, Koerner Hall’s ducts span metres, which helps keep the ventilation system silent. (Imagine blowing air through a straw versus through a subway tunnel.) In addition, the basement air-conditioning unit is located in a separate building, beyond the acoustic barrier of the hall.
Dampening effects: For amplified events, the loudspeakers are exposed and the acoustic curtains are extended to absorb sound more quickly, reducing the reverberation and increasing the clarity of the audio.
KOERNER HALL: BY THE NUMBERS
13,000: Approximate square footage of ¾”oak flooring in the hall stage and audience area
175: Largest number of people who have performed in the hall at one time
165: Total number of rubber pads (varying in dimension) used to support and laterally restrain the entire concert hall, 114 of which support the full building weight or gravity load. The other 51 pads provide lateral or earthquake and wind resistance to keep the building on the pads.
17.5 million: Total building load in pounds.