On a bright summer day in Lower Manhattan, U.S. District Court Judge William H. Barbour, Jr., huddles with GSA officials in a dark, soundproof room no larger than a storage closet on the 12th floor of Arup's New York office. The group listens intently to testimony from a witness, then questions from the defense counsel, and finally commentary from the judge.
For once, Barbour is not concerned with the facts of the case, the arguments of legal teams, or the outcome of the trial. In this case, he's focused on one thing: how clearly he and his peers in the District Court for the Southern District of Mississippi will hear trials in their soon-to-be-constructed courthouse in Jackson.
Judge Barbour and the design team for the $90 million federal courthouse in Jackson, to be completed in 2009, are participating in a GSA pilot study that is applying advanced auralization techniques to refine the acoustical qualities of federal courtrooms.
GSA commissioned Arup's SoundLab—a state-of-the-art sound-testing lab for built environments in the firm's New York office—to model the design of the Jackson courtrooms, as well as planned courtrooms in Buffalo, N.Y.; Eugene, Ore.; and Gulfport, Miss. The goal is to improve speech intelligibility, minimize background noise, and optimize reverberation in these spaces.
Getting the acoustics right in courtrooms can be tricky, said Joe Solway, senior consultant with ArupAcoustics, the sound engineering division of international engineer Arup, during my visit to the SoundLab last month.
“The GSA wants courtrooms to be big grand spaces, so they set a minimum ceiling height of 16 feet,” he said. High ceilings often result in greater reverberation, which makes it difficult to meet the stringent speech requirements mandated by the GSA in its U.S. Courts Design Guide.
“One is playing against the other,” said Solway. “What often happens is the design team ends up relying on amplification systems to meet the standard.”
By modeling the spaces during the design phase, Building Teams and their clients can test out various configurations and tweak the design to improve acoustic performance. Early testing of the Jackson courthouse, for instance, showed that a curved wall at the rear of the main courtroom was causing undesirable reverb times, affecting speech intelligibility. The front wall behind the judge's bench was also a problem.
“We tested all types of generic sound-absorbing material on those walls until we got it just right,” said Solway. The final solution reduced the reverb time from 1.1 seconds to 0.7 seconds. The difference is akin to hearing a muffled, unintelligible voice versus crisp, clear speech. “The result is a design that promotes early reflection without late reverberation, resulting in increased speech intelligibility,” says Solway.
Sight and sound coming together
Arup's role in the Jackson courthouse project extends beyond acoustics. GSA officials were also interested in modeling the lighting scheme and architectural design of the courtrooms in a 3-D virtual-reality environment. This would enable the Building Team to test the design for lighting, sightlines, and interior finishes without having to construct full-scale physical mockups—a requirement for all GSA courthouse projects, until now—which can cost $250,000-$500,000 for a typical courtroom project.
“Mockups are good for testing sightlines, but they don't allow teams to assess the lighting and acoustics,” said Solway.
The high-resolution 3-D model created by ArupLighting, in collaboration with the firm's 3D Media group, allowed users to navigate the courtroom, checking for sightline obstructions, lighting glare, and other design miscues. The model was accurate down to the luminaire model and traits of the finishes (color, texture, etc.) based on data from the design team and manufacturers.
The design team, which includes design architect H3 Hardy Collaboration Architecture, New York, navigated the virtual courtroom searching for possible design flaws. While the initial design was sound, the team noticed several issues associated with the lighting scheme, including glare on the judge's bench and distracting “hot spots” near the witness box. The scheme was altered and then re-modeled by Arup engineers until the team was satisfied with the final product.
“The savings far covered the cost of creating the model,” said Solway. The model was programmed for roughly half the cost and in a fraction of the time of building a physical mockup.
What's next for SoundLab?
Solway says in the near future clients will be able to walk through a fully simulated model of courtroom spaces. Additions such as wrap-around monitors will create a more realistic environment for testing simulations. Models may also incorporate cutting-edge technology like mass-evacuation modeling for simulating the reaction of building occupants during an emergency evacuation.
“We will immerse clients in this very accurate virtual environment, where they can test acoustics, lighting, and sightlines simultaneously,” says Solway.