Tuesday, June 20, 2000
How to fill a music museum with sound without sending people out the door screaming
by Melinda Bargreen
Seattle Times music critic
As the distinctive, love-it-or-hate it profile of the Experience Music Project took shape, passers-by knew one thing for sure: There's never been a building exactly like this one.
Acousticians knew it, too. Project acoustician Mark Holden, of Jaffe Holden Scarbrough Acoustics, knew he and his company had a world-class challenge in store. The task of containing, controlling and focusing the sound in all the undulating, curving portions of the EMP building was certainly going to push the acoustical envelope, in a profession usually dedicated to more traditional concert-hall design.
"Our whole philosophy on EMP was, 'Let's think about a different paradigm,' " Holden says.
"We had to look at every surface and every material and decide how it would react to sound, and then to fine-tune the result. We started our work at the very earliest stages of the design concept, working on everything from the interior of the skin of the building to all the other spaces. We're talking about a building with 140,000 square feet, full of curved and potentially troublesome walls and ceilings.
"From our earliest talks with Ann Frank Farrington, director of exhibits, we began to imagine spaces where visitors would learn listening skills and be able to create music without any distractions - in exhibits that didn't have walls or doors or visible means of acoustic baffling."
This also meant that while one exhibit would feature sound levels approaching live-concert intensity, a nearby exhibit would require near-silence for the visitor to evaluate the differences in the sounds of guitars. Building codes, and EMP's own mandate for open and inviting design, meant that closed-off recording booths and studios were not good options. Nor was it possible to place baffles, soundproofing and other acoustical materials on the undulating, swooping lines of the building, whose walls, ceilings and steel-beam ribs were to remain visible.
The acoustical mandate was not only to maximize good sound, but to minimize the loud omnidirectional sound produced by the visitors themselves. Holden didn't want to create a situation similar to the one they were called in to fix at the St. Louis Zoo, where a hexagonal room called "The Living World" had sound sources blasting in so many directions that visitors "sprinted out after about a minute in the room, not understanding anything, the adults holding their ears and the kids screaming."
Holden and his technical assistants worked closely with Frank Gehry's interior-space team to fine-tune the sound in the lobby, so that instructions over the loudspeakers ("Bus Seven, meet over here," as Holden puts it) could be clearly understood.
The biggest single challenge?
"The sound lab," Holden says immediately.
"This was certainly the single most challenging acoustical space. It involves everything from a professional recording studio to a space that gives an individual acoustic experience. Visitors make music like a professional, replicating the studio-like environment without a real studio and all the physical accoutrements like thick walls, heavy padding and thick doors. We were just working with open spaces, not boxed or closed-in rooms. We needed to provide an open-air experience, a 'sound platform' in each sound pod that would provide many different kinds of sonic experience to the visitor."
Holden uses what he calls "trade secrets" to fool the ear into believing the sound is louder and different from what the ears actually are receiving. By placing loudspeakers in each sound pod as close to the listener's ears as possible, and doing some tricks with sound processing (adding echo and other effects) to "fatten and sweeten" the sound, the illusion of a bigger, louder sound is created. Human hearing also can be fooled by the perception of vibrations underfoot; Holden's team creates the illusion of a booming bass by making the floor vibrate.
At the same time, unwanted sound in other areas was damped with acoustic treatment on walls, floors and ceilings, including stick-on substances similar to linoleum (on metal panels), and acoustic batting (behind the "Snake Wall" that threads through the public spaces).
One of the most fascinating challenges was dealing with Gehry's purple aluminum wall panels that make up the three visible walls of the big Sky Church. How would these panels react to concert-sound levels? The acoustical team tested them at the well-known Riverbank Acoustics Test Labs, founded in the 1800s by Wallace Sabine, the father of modern acoustics and designer of the sound in Boston Symphony Hall.
As the first 6-by-9-foot panel was tested, a strange phenomenon was observed: The panels were "singing" in response to the "pink noise" test signal (that's akin to "white noise," except with "more balance in the energy and more bass," according to Holden). The panel was bowing and reverberating in the manner of a bent musical saw. Some members of the acoustical team claimed that Jimi Hendrix's musical spirit was to blame - but less fanciful listeners are waiting for a clearer manifestation.