This week, a new sound will resonate through the handsomely refurbished and greatly expanded Orchestra Hall. Will it be a better sound? That’s the $110 million question.
In 1904, architect Daniel Burnham and Chicago Symphony Orchestra founder and music director Theodore Thomas collaborated to create the beaux arts-style auditorium on Michigan Avenue. Their efforts produced a hall whose dry, inconsistent sound has frustrated musicians and dismayed listeners.
Over the years, there have been many half-hearted attempts to improve the acoustics. This time around, the CSO hired Kirkegaard and Associates of Downers Grove, one of the world’s leading architectural acoustics firms. The company analyzed everything from the way sound moves around the hall to how the seats are made.
To help readers understand the most important acoustical changes and modifications, we offer this tour of the renovated Orchestra Hall.
SYMPHONY CENTER
An expanded music facility
Changes invisible to the eye, not the ear
Much of the interior of Orchestra Hall will look the same as it did before its renovation, but nearly everything in and above the hall was modified to improve its acoustics.
PROBLEMS WITH OLD ORCHESTRA HALL
A The limited amount of attic space in the hall and steep balconies prevented sound from resonating properly.
B Heating and cooling equipment on roof and over stage shell generated background noise.
C Sound quality varied throughout the hall, especially on the main floor.
D The shape and material construction of the stage directed sound away from musicians.
Improvements in the new hall
THE ATTIC
1 Increased space (by about 50 percent) for sound to travel by raising the roof 25 feet.
2 Relocated the heating, cooling and electrical systems to another building to prevent unwanted noise and vibrations from entering hall.
3 Replaced rectangular heating and cooling ducts with round ones that better reflect sound.
4 Installed heavy plaster and concrete reflectors (two above the audience ceiling and one above the stage) to redirect sound to the audience.
THE WALL
5 Rebuilt all walls and moldings with thicker plaster to better reflect sound.
Plaster thickness:
OLD 1″ TO 2″ THICK
NEW 2″ TO 4″ THICK
6 Replaced plaster from areas in the side walls with “acoustically transparent” perforated metal sheets that sound can pass through, allowing it to enter space above and behind it for better reverberation.
7 Tilted and reshaped walls on main floor to direct sound farther back into the hall.
THE CANOPY
8 Installed an acoustical canopy to reflect sound back to musicians and out to audience.
The glass and steel canopy weighs 14.000 pounds and is held in place by cables that connect to a device on the top floor that can raise or lower canopy as needed.
THE STAGE
9 Installed sound diffusors behind the stage to better reflect sound back to musicians andinto the new space above the stage.
The angles of the reflectors and the size of the diffusor were determined after testing sound movement on a model of the hall.
10 To add space, the stage was extended back 16 feet and outfitted with a heavy, sound-reflecting wooden risers to improve sightlines.
Perforated metal has been used in the stage shell for years to help sound distribution.
THE SEATS
11 Raised several rows of seats at the back of the main floor to improve sound reception and sightlines.
Reduced the amount of foam in the seat cushion and chair back to reduce sound absorption.
12 The reconfiguration of the hall and the use of wider chairs (for comfort only), reduced the number of seats by 272, but the addition of terrace seating around the stage helped offset the loss.
Seating in hall: OLD: 2,582 NEW 2,310
NEW FABRIC
Replaced velour-like fabric on seats with a wool/cotton blend that minimizes sound absorption.
How the new design improves acoustics
Because sound travels in all directions at once and at a constant speed, a hall with unbalanced design elements can distort how sound is heard.
BEFORE RENOVATION
The hall’s short stage and angled walls prevented sound from being heard uniformly around the hall (called variability) while the lack of overall space for sound to reverberate accounted for its so-called dryness.
AFTER RENOVATION
By raising the roof, refinishing the hall’s many surfaces and adding an acoustical canopy, sound can now be distributed more evenly. Whereas the old hall suffered from a short reverberation time (only 1.2 seconds), the new hall has been configured to have a reverberation time of 2 secondsa time on par with the world’s highest-rated concert halls.
Sources: Dawn Schuette at Kirkegaard & Associates; “Concert and Opera Halls,” by Leo Beranek; Skidmore, Owings & Merrill.
