"Tower of Voices," a 93-foot musical instrument at the Flight 93 National Memorial, honors the passengers and flight crew who decided to fight back after terrorists hijacked their United Airlines plane on Sept. 11, 2001. The plane crashed in a field near Shanksville, Pennsylvania, never reaching its intended target but killing all on board.
The monument, pictured above during a rainy dedication ceremony on Sept. 9, contains 40 wind chimes, one for each person aboard the flight.
Each of the chimes has a unique tone to represent each person on the flight. The sound of the chimes is audible only to those near the memorial, serving as a visible reminder elsewhere on the memorial grounds near Shanksville and nearby U.S. Route 30. The monument is the final piece of the 2,200-acre park dedicated to the flight.
You can hear a simulation of what the tower's chimes will sound like in the SoundCloud embed below:
Upon learning the flight had been hijacked, the passengers and crew aboard the plane made phone calls, some leaving voicemails, others learning about the planes that had already been flown into the World Trade Center towers. With that knowledge, they decided to fight back and prevent the plane from being used for a similar purpose. In the ensuing struggle, the plane crashed, killing everyone on board.
Elizabeth Valmont, the acoustics group leader for the firm Arup that assisted with the sound design of the tower, cited the audible nature of the memorial as key to honoring those who died when the flight crashed not far from where the memorial park stands now.
"Each wind chime has a distinct tone due to its length, tuning and placement in the tower," Valmont told Architect Magazine, "representing the critical and lasting role of the voices heard through phone calls and voicemails that took place during the flight."
You can learn more about the tower's construction in this eight-year time-lapse video:
Editor's note: This story has been updated since it was published in September 2018.