Musical Accompaniment
- By Julie Sturgeon
- 08/01/04
Once upon a time, acoustics meant choosing between the mineral fiber ceiling tiles and fiberglass ceiling tiles. Today, college administrators tackling a new performance center on campus have a range of downright cool materials to play with: perforated metals and woods to modeling software that allows you to hear your choices before you commit.
Unfortunately, many architects don't take acoustics in school. So members of the Acoustical Society of America have reached out in the past 10 years to remedy this knowledge gap in the construction industry, running around the world, listening to theaters from Vienna to Boston to Los Angeles. After establishing objective metrics to record things like reverberation ("K time" for insiders), clarity levels and envelopment, these scientists have related their numbers back to the buildings' architectures and begun publishing the results. (Leo Beranek leads the offerings at bookstores across the country.)
So before administrators can talk options, it helps to know how to talk sound science, says Kenneth Roy, senior principle research scientist for Armstrong Ceiling Systems. Acoustics boil down to a balanced combination of absorption and reflection. Absorption is exactly what it appears - unless the materials soak up some of the sound, the reverberations become too loud to function. Drywall, for instance, would bounce those sound waves until the results resembled screaming more than singing. If the room will host teaching as well, speech intelligibility requires a much lower reverberation time.
Sound reflection is the important ingredient to generate a feeling of spaciousness in the room. Sound coming from the sides in particular creates a desired enveloping sensation, Roy assures, but a roomful of reflective materials, especially in the back of the hall, creates nothing but a cavernous echo. So acoustical scientists employ three-dimensional diffusing techniques to scatter the sound that comes in at a specific angle back out over a lot of different bends. The level remains high, but without the directionality it eliminates echoes.
Today's top-notch performance arenas want to set up the stage as a relatively reflective area, with reflective side walls toward the front to promote sound envelopment. Small theaters - which Roy admits he can't define in terms of straight square footage, thanks to other factors like volume - work best with sound absorption in the back; larger venues opt for diffusing elements instead.
Donna Barry, vice president of Gould Evans in Phoenix, Ariz., checks out the dynamics in a very visual way: She builds a model and shines a laser pointer on the back walls to determine whether the angle and materials reflect sound properly.
The Beauty of Sound
The excitement for college administrators lies in the reflecting/diffusing category, according to Roy. Thanks to perforated metals and woods, the aesthetic options for performance centers are wide open. Because the specifications are usually at least one half in. thick, all woods can handle the reflection job - so choose between cherry, maple and oak without ramifications. "The amount of perforations you put into the wood, how you apply it to the wall system and whether you have a nonwoven high air-flow resistance or fiberglass behind the skrim determines how much it will absorb," he says. Ditto the metals: everything from shiny brass to painted tiles is on the drawing board.
"Some of these richer materials really add to the aesthetics because they're warm, rich and very signature. It's just that now they're very functional with acoustics, also," Roy says. "And, we're really just getting started!"
Thanks to this explosion of choices, college administrators have several good models to study, with more coming online every day. Barry points to theaters Evans Gould recently completed for Dixie College in Utah as a good example. The Center for Fine and Performing Arts at Owens Community College in Perrysburg, Ohio and The George S. and Dolores Doré Eccles Center for the Performing Arts and Horne School of Music at Snow College (also in Utah) stand as good role models, too.
The list soon could grow even longer. Architects are perfectly capable of using these materials and theories to remodel existing halls as opposed to razing the structure and starting anew, Roy tells clients. In fact, within the next few years, university officials easily could find themselves on the hot seat without an upgrade. "Universities work with people who will someday be performing in the great venues. You must refine your techniques within the kind of architectural space you'll actually play in," he points out.
Barry agrees, noting that even the most uninformed audiences can tell the audio difference between a room with quality acoustics and one without. And, today's shows increasingly require multimedia, a wrinkle that cries out for upgrades in equipment and sound perception."
The elephant in the room, of course, is the fact that widening choices mean specialization, which translates to a need for more than one performing venue. "One size never fits all," Barry warns. For instance, choral music requires a large reverberant cavity for a lofty sound. Dialogue in a play simply shouldn't float around the room like that. "It's like going to see a hockey game in a football arena. The sight lines are different - it's just a different animal. So you can make things fit, but it's best if you have a recital hall for music and a theater built for drama." Because colleges work with notoriously tight budgets, she has found success so far working with acoustic drapes and other fabrics to manipulate the space quickly.
A Sneak Preview
Confused? Architects today can walk you through the process painlessly using software like Ease. Roy has relied on this technology since 1995 to convert CAD drawings to electronically produce a proposed room's impulse response, then play the sound you'd hear under different conditions he specifies. (You can also plug in existing buildings to this software; Roy recalls fiddling with it to see how he could manipulate a standard gymnasium with a 30-ft.-high ceiling.)
Technology also charges to the rescue on the finished products. Some companies offer practice rooms so highly absorptive they offer no characteristics of their own. Add in speakers with digital signal processing and voila! You've instantly whisked performers to a specific hall. Students hear themselves just as if they'd purchased an airline ticket and flew to Carnegie Hall for one song and the Vienna Opera House for the next number.
"You should definitely offer acoustics at least as good as some of the civic performances," is Barry's rule of thumb. "Especially in the college market. That's where they're learning how to project their voices, how to use the equipment - these spaces are as important for learning as for performances."