When the Arena Stage theater opened in 1961, the handful of flights in and out of nearby Ronald Reagan International Airport in Washington, D.C., weren’t such a big deal. Today, there’s a near-constant roar overhead. But exterior sound isn’t the only challenge. Architect Bing Thom, brought in to rework the space and add a new “cradle” stage (for plays in development), decided to take the term literally, creating a rounded space that engulfs the audience. The result, however, was an acoustically difficult shape. Thom, with acoustical engineer Richard Talaske, dotted the theater with woven shapes that absorb sound. The spiraling hallway around the cradle lends sound isolation, as does the glass-and-timber layer that forms the building’s exterior. Now the audience only experiences the sounds that it should.