The Tower of Voices, the wind chime at the Flight 93 National Memorial, is one of the few memorials that incorporates sound.
Acoustical experts struggled to find a way to make each of the 40 chimes different, yet harmonious, and to find a way to protect them from the elements, while letting the wind work the chimes. The 5′-9′ chimes act as bells, with strikers within the tubes, a new concept.
More than two years of work went into the chimes and those who worked on them suspect that sound will become important to future memorials.
Read more from Popular Science’s Eleanor Cummins here.