By Ruth Evans

Click here to listen to the documentary: A Memorial in Sound

On television screens across the world the World Trade Center appeared to collapse silently and surreally, punctuated only by the total disbelief of commentators trying to comprehend what their eyes were seeing.

The awful reality was anything but silent of course.

A tourist poses for a picture near the towers

As they watched the confetti of paper and memos fluttering down into the dust the Kitchen Sisters - also known as Nikki Silva and Davia Nelson - began thinking of all the ephemeral noises and voices that made up day-to-day life in the Twin Towers.

In a bid to preserve the World Trade Center in sound they, together with National Public Radio, began to collect material for what was to become the "Sonic Memorial Project."

A special phone line was set up and they asked the public for their stories, recordings, remembrances, oral histories, video and any sounds related to the life and history of the World Trade Center.

Overwhelming response

Over the past year, thousands of people have called in or contributed their audio memories, recordings and artefacts.

The archive records the construction of the WTC

By preserving the acoustics of everyday life within the towers the Kitchen Sisters have painted a portrait in sound.

Daria describes the project as being like a Pandora's box: "A door opened and one thing led to another".

Both Nikki and Davia have been amazed by the material that came to light and how generous people have been in sharing these recordings.

Daria says: "Everyone tried to think this idea out - what would it mean to create a memorial that didn't have a physical presence.

"Most of our memorials are mute and don't speak to us, but we envisaged this being a little like the Aids quilt, with everyone contributing a square of sound and together we stitched this vast audio memorial quilt."

Remembering the lost

Every floor had so many stories; each tower had so many sounds.

One woman said that each time she had entered the World Trade Center the sound of the revolving doors reminded her of a heart beating.

A jogger described the sounds of the restaurants reverberating around the cove of the building.

A couple tie the knot in the WTC

Another caller said that at night the building echoed with Latin American music from the radios of the cleaners, many of whom were illegal immigrants from Mexico and perhaps have never been accounted for.

Of the hundreds of calls that came in, many were also tales of romance and marriage that took place in the World Trade Center over the past 30 years.

Most of the messages concentrated more on life than on death, painting an aural history of the twin towers.

"It has been a very difficult project for both of us to work on" says Nikki "The material was very raw and moving."

The calls spoke of the insistence of memory, of glamorous New Years Eve parties and song, of the energetic hum of busy buildings, urgent whispered messages, vocal expressions of loving and grieving - all of it an antidote to silence.

The Sonic memorial will continue to be collated and will be stored at the George Mason University Digital archive so that the public can access it.

Pictures courtesy of Charles H Traub, Jane Selewach, Kanien Kehaka Onkwaw�nna Raotitiohkwa and Mr & Mrs Krutzel.