The measured ambient noise level inside Disney Hall — the sound when nothing is happening — ranged from 24 to 28 decibels, according to the environmental report. It said Federal Transportation Authority noise standards call for a transit impact on concert halls of no more than 25 decibels— and that abatement measures will ensure that two passing trains project just 16 decibels into Disney Hall.
Pennington said that setting a speed limit lower than the 15 mph anticipated near Disney Hall also would reduce noise, but he doesn't expect that will be necessary.
Metro already has met the challenge of protecting recording studios in Hollywood from noise along its Red Line subway, he noted, even though the rail cars are heavier, and their vibrations bigger, than the ones that will run near Disney Hall.
Toyota, Disney Hall's acoustical designer, said that that the foundations of subway-adjacent performance halls he worked on in Tokyo and Shanghai have special features that reduce ground vibrations, but not Disney Hall. Widely acclaimed for its superior sound since opening in 2003, Gehry's space and Toyota's acoustics provided a platform for the Los Angeles Philharmonic to attract superstar conductor Gustavo Dudamel as its music director.
"We didn't assume a big vibration, such as from a subway, was going to come," Toyota said, and there's nothing further that can be done to the building now.
Deborah Borda, president of the philharmonic, said she isn't alarmed by the recent Colburn School noise simulation but thinks it's helpful that it has brought increased awareness.
"I think it's a good thing that there's a certain amount of uproar.... I have a comfort level with the [planning] process to this point, but the process is not completed," she said. "We all agree more analysis is required. [Disney Hall] is a treasure that has to be protected and maintained, and it will be."
Colburn School's president, Sel Kardan, issued a statement saying "we are working in a positive way" with Metro officials to keep its music facilities free from subway noise.
Yaroslavksy, a classical music buff, said the task now is "to determine whether the 2011 studies are valid or something slipped through the cracks. I'm not going to prejudge it or get hysterical about it. Obviously Metro will not build a line that is going to compromise Disney Hall."
Until reports of the Colburn School simulation began to circulate, "everybody was in sync" about the subway not being a noise threat, Yaroslavsky said. "If they're not in sync now, we'll get to the bottom of it. We want to find out what the facts are, and if the truth is that vibrations may compromise the acoustics of Disney Hall, Metro is going to have to adjust accordingly."