ST. PETERSBURG — In total silence, one of the world's foremost acousticians bent over a sound board and slid a button forward. Then he listened as a swooping noise came out of a huge portable speaker on the stage of the Mahaffey Theater, from low to high, like a signal from space.Rick Talaske, 65, was testing a new, $1.8 million acoustic "shell" his Chicago firm designed for the Florida Orchestra. To the audience, the eight panels stretching high above the stage might look like a rear wall. But they can be moved, as can a 4-inch thick, pockmarked ceilinglike structure that weighs several tons and hangs over the musicians. Both parts of the shell should enhance both the audience's ability to hear the orchestra clearly, and help musicians to hear each other.The goal, Talaske said, is to "allow musicians to create the most beautiful music."The orchestra, which opens its 50th season this weekend with the Carmina Burana, has waited four years for this day. That's when a plan was hatched to replace the existing shell, installed more than 30 years ago in what was then the Bayfront Center. The city of St. Petersburg, which owns the Mahaffey, paid for this one using Penny for Pinellas funds and a state grant."This is a special moment," orchestra president Michael Pastreich said. "This is something that the orchestra has needed to do for decades."That's because when it comes to acoustics, the worst seats in the house are the ones musicians are sitting on. They live in a cacophonous world, in which sounds blast so loudly they can become hard to distinguish. The panels of Talaske's shell cover more space and sit farther away than did the old shell, improving the way sound returns to musicians from their instruments and those of their peers."When a bass player plays on the left side of the stage, the violin on the right side of the stage will hear those notes much more clearly than they would have," Pastreich said.Angled canopies of medium-density fiberboard, hanging about 15 feet above the floor and extending toward the audience, also serve a key function. The old shell also had two ceiling structures, but the upper one had broken over time and was removed altogether during renovations in 2006, Pastreich said."A lot of our sound was going up into that stage house and never making it into the audience," he said.Other acts performing at the Mahaffey could theoretically use the shell, but the orchestra needs it the most. They started with a design manufacturers at the Wenger Corp., a Minnesota company, referred to as its "diva" shell. To Pastreich, that was just the chassis around which to build a car. Consultants from Fisher Dachs, a theater design firm, and ARC3 Architects were brought in to work out every detail, down to what type of hinges would hold the ceiling together. Workers finished installing the shell Monday. Talaske wrapped up his tests Tuesday morning, studying a graph on his iPad. The graph consisted of thin lines, like scores of stalagmites representing what he calls "articulations of sound" traveling across the stage. Close to two dozen of these lines crowded into less than an inch of space on the iPad — covering a total of 1/20th of a second."That makes me happy," Talaske said.Contact Andrew Meacham at [email protected] or (727) 892-2248. Follow @torch437.