For the third and final phase of the Flight 93 National Memorial, scheduled to open on Sept. 9 in Shanksville, Penn., architect Paul Murdoch assembled a team like no other.

The project, a 93-foot tall Tower of Voices, required the usual civil engineers, structural engineers and lighting experts. Then there were the wind engineer, the acoustical engineer and the musician who understood which of its 40 notes to bring together.

“We also needed a type of structural engineer who deals with moving mechanisms and dynamic forces, because the chime mechanism is our biggest technical challenge to work out,” Murdoch says.

The tower’s meant to be ever-changing with natural forces, and a one-of-kind experience for visitors at any time of day or season. There are different moods from different conditions on site.

“We’re trying to achieve that in terms of sound because it’s changing with the wind with a lot different qualities with the sound,” he says. “The winter wind is quite severe, at 30 to 40 miles per hour from the northwest, and the rest of the year it comes from different directions and lower wind speeds.”

The tower is designed to commemorate the words and voices on cell phones aboard United Flight 93, hijacked by terrorists on Sept. 11, 2001, bound for Washington, D.C. and plowed into the ground when passengers sought to take back the cockpit.

It’s a solemn business, this tower design. It’s meant to move the visitors on approach, walking through and participating in the landscape design by Nelson Byrd Woltz.

“There’s a plaza on a raised mound in a field that’s the place to listen to and be one with the tower,” Murdoch says. “The intent is not to have a booming experience with sound but a more intimate, contemplative and reflective experience – it sets the tone for the memorial.”

Murdoch and his teams have been working on the project with the National Park Service for 12 years, phasing in the landscape design and visitors center first. The tower is the crowning achievement on a number of levels.

“It sets the tone for the memorial,” he says. “It’s meant to be heroic in stature but intimate in personal experience.”

Just like the 40 passengers and crew members aboard Flight 93.

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