Paris (AFP)

"The organ must find its little acoustic cocoon": Mylène Pardoen, archaeologist soundscapes, was sent to the bedside of Notre-Dame de Paris to restore the "strange sound" of the cathedral partly burned.

Like the light filtered by stained glass or the very special smell of candles, the sounds of a cathedral are part of its DNA. The acoustics of such a place depend on its architecture, the materials used, the chosen furniture ... but also the surrounding urban fabric.

"Every church, every cathedral has its unique acoustics, its little particular feeling", explains to AFP Mylène Pardoen, research engineer at the Institute of Human Sciences (ISH) of Lyon.

A wooden element, for example, will not sound like a stone.

At Notre-Dame, this unique cocktail went up in smoke on April 15 when the fire left the cathedral with three important holes in its vault.

"Now, there is more of her!", Regrets Mylène Pardoen, just the external noises that go through the holes, the fuss of robots that support the workers or vacuum cleaners ...

From her first visit to the burned cathedral in July, the specialist also retains the smell of "burnt wood, melted lead" and the high brightness due to holes in the roof and the absence of stained glass.

The CNRS scientist, passionate about history, coordinates the acoustic group of the "CNRS Notre-Dame project", missioned for five years. The role of these experts: identify the best restoration strategies for the cathedral to regain its original acoustics.

For this, Mylène Pardoen and her colleague Brian Katz, acoustician, have a 2013 acoustic survey, their point of departure.

- "Go back in time" -

The engineer will also "go back in time". With the help of specialists and historians, she will recreate the interior and exterior of the cathedral and deduce "the soundscapes of Notre-Dame for a given time".

A painstaking work because the location and size of the chapels could change, the aisles be moved, cornices and furniture altered. Even the urban fabric is today completely different, the forecourt for example was much smaller. "All of this has a direct impact on what you can hear."

Then using a virtual model, the two specialists will be able to predict how to fill in the holes, in particular to guide the choice of quarries where the stones for the vault will be taken.

"When we know who has won the various tenders, we will go to see the selected artisans and we will also take readings for each validated work, whether on the vault or on something else, to readjust the model and say that can go where it can not go, "she describes.

The sound experts will also make "recommendations", even if the final choice will not be their responsibility: "The scientist does not have the hand on politics".

Mylène Pardoen thinks she can start surveying in the cathedral at the end of October, beginning of November.

In the meantime, he will have to find the funding, especially for the material that can not come out of the cathedral because it will be "polluted". "There is no porosity between what has been given and our work," she says, so there is no question of benefit from the many donations made after the fire.

But what is certain is that it will do its best to make the sounds rediscover their flavors before the drama. Especially for the chorus and the organ: "The instrument was built almost to measure, for a given acoustics," she says. "It's about musical heritage".

© 2019 AFP