Updated

There are prominent videos of the twin towers collapsing, photos of people falling from them and voice mail messages from people in hijacked planes.

But behind the wrenching sights and sounds of the National Sept. 11 Memorial Museum lies a quiet effort to help visitors handle its potentially traumatic impact. American Red Cross counseling volunteers will even standing by as it opens to the public Wednesday.

One designer who helped create the exhibits says "there's a lot of thought given to the psychological safety of visitors."

There are built-in tissue boxes and a layout designed to let people bypass the most intense exhibits if they choose. Discreet oak-leaf symbols denote items connected to the dead, and images of falling victims are in an alcove with a warning sign.