Nothing in the Los Angeles Philharmonic's repertoire calls for 135-ton trains. The orchestra aims to keep it that way when Metro light rail cars start rumbling through a subway tunnel near Walt Disney Concert Hall.
Experts who know the hall's acoustics are worried that the listening experience in the main auditorium could suffer when subway trains begin running 125 feet below the parking garage in 2020.
"It would be a disaster for Disney Hall," said its architect, Frank Gehry.
Subway planners have assured that noise won't be a problem, but a recent simulation conducted by the Los Angeles County Metropolitan Transportation Authority raised concerns.
The acoustic experiment was conducted April 23 in Thayer Hall, a below-ground performance and recording space at the Colburn School. The intimate venue, near 2nd Street and Grand Avenue, is closer than Disney Hall to the $1.37-billion subway's route, which will include a stretch beneath 2nd Street from Hope Street to Central Avenue.
"They played a solo piano piece through a loudspeaker and had subwoofers that simulated a passing train," said Fred Vogler, a recording engineer who oversees recording sessions and concert-taping for the Colburn School and the L.A. Philharmonic. "The test was several minutes long. Then they said, 'Is anybody troubled by the train sounds?' We said, 'Well, we heard them, if that's what you're asking.' It set off a lot of concerns."
Gehry heard about the test from Vogler, then passed along his concerns to Los Angeles County Board of Supervisors member Zev Yaroslavsky and others. He said projections of subway noise done nearly two years ago by Metro's noise abatement consultants, who predicted there would be no audible impact on Disney Hall, should be reviewed.
"The flag is up, and we should go over it and make sure," the architect said.
Art Leahy, Metro's chief executive, said that the simulation didn't represent the actual expected sonic impact of the trains. He said it was part of the process of determining just how exacting the noise abatement devices along the tracks must be to meet Metro's goal, which is no additional noise at all in performance spaces near the subway. In addition to noise-abatement consultants, Metro has hired an acoustics expert.
"We are not about to do anything which in any fashion, however slightly, impairs or damages … Disney Hall or any other feature in that area," Leahy said. "They are critically important, and we are simply not going to build something that reduces the utility or benefit of those facilities. That's a blanket statement, no conditions or qualifiers on it."
The standard to be met isn't just preventing noise that an audience can hear, Leahy said, but the more stringent one of eliminating sounds that a recording microphone can pick up.
Yaroslavsky and Stephen Rountree, president of Disney Hall's landlord, the Music Center, said they will arrange a meeting in which cultural organizations adjacent to the subway route, which include the upcoming Broad Collection contemporary art museum and REDCAT, can receive an update from Metro project officials.
Rountree said the Music Center is retaining Disney Hall's acoustical designer, Yasuhisa Toyota, and its original noise abatement engineer, Charles M. Salter Associates, to go over Metro's noise projections, which raised no concerns when presented to cultural leaders in fall 2011.
"If new information has come up, we want to make sure it is reassessed and taken into account," Rountree said. "We'll bring in the engineers and go through the numbers one more time and make sure everyone is comfortable."
The sound simulation at Colburn was aimed at establishing the threshold at which subway noise ceases to be a problem, said Metro's Bryan Pennington, executive officer for the Regional Connector Transit Corridor Project, which will lay 1.9 miles of underground track to connect the Blue Line and Expo Line with the Gold Line.
The testing will help Metro set the maximum allowable decibel level for each performance space, which the subway's eventual design and construction contractors will have to satisfy.
Pennington said a June simulation at Thayer Hall will be at 36 decibels, down from 39 decibels in April. Lowering a sound by 10 decibels makes it seem half as loud. He expects construction to begin at 2nd and Grand in two to three years. The project depends largely on federal funding that Metro hopes to land by the end of 2013.
The Environmental Impact Report, approved by the Metro board in January 2012, calls for common noise abatement features that reduce vibrations from passing trains, including rubber cushioning beneath the tracks, and rubberized fasteners to hold them in place. The result, it predicts, will be no audible impact on the nearby performance spaces.