Notre Dame is back. As well as its acoustics.
The Paris cathedral, which burned dramatically in a fire in 2019, will reopen to the public on December 8. After the fire, acoustic researcher Brian Katz studied the sonic qualities of the cathedral, such as the reverberations and reverberations created. from the space, both after the restoration and in different periods of the centuries-old history of the cathedral (SN: 1/12/20).
Before the fire, Notre Dame was reverberant, meaning that noises would hang in the air for several seconds before dying out, due to sound waves bouncing off the walls, floor and other surfaces within the massive space. That echo was drowned out by the fire, which left holes in the vaulted ceiling and debris and ashes spilling onto the floor. Now, after repairs to the structure and cleaning to remove toxic lead and other dust released in the fire, the cathedral is closer to its former self. But even seemingly small changes in a space, such as wall hangings, carpets or furniture, can change its acoustics.
Scientific news spoke to Katz, from the CNRS and Sorbonne University in Paris, about his work and how he expects the revitalized cathedral to sound. This interview has been edited for length and clarity.
SN: How are the acoustics of Notre Dame now?
Katz: We were there at the end of September to take some progress measurements. There was still a lot of construction work. Especially seeing how much has been cleaned up since then, we’re really hoping to get in there in the next couple of weeks to take some actual condition measurements.
Feedback from the few who have been there [more recently] it’s, “Wow, that’s a lot of echo there.” I think we all expect it to resonate [compared to before the fire] because it is clean and refined. Every surface was sprayed with latex [that was later peeled off] which absorbed and absorbed the lead from the pores in the stone. Well, it also absorbed all the other dust and everything, so it’s extremely clean. All that residual absorption that comes from dust and dirt over the years is gone, so it should be a very lively sounding place.
SN: What are the criteria for good acoustics in a space like Notre Dame?
Katz: As for the sermons, they have a whole new sound system that has been modernized. And the sound system is really designed to minimize the amount of sound energy that is sent into the reverberation space and really focus on the audience. So this should really help intelligibility even in a reverberant space.
[For performers not covered by that sound system] It’s mostly about the style of music and what’s the right echo for what they want to play. I would be very excited to see something like that [allows] variable acoustics, a way to rotate tapestries in and out so that they can say: We want a more lively space or a more restrained space keeping with the aesthetics. I think that would be ideal.
SN: How were acoustics considered during the renovation?
Katz: When the decision was made to restore the cathedral as it was before the fire, you didn’t have to decide: “What impact does it have? [on the acoustics] if we put a limestone arch here?” because there was one there before. Before that decision was made, the question was, “What if we make that limestone arch out of glass?” or “What if we really changed things?”
So now that takes a lot of the guesswork out, and now it’s more the impact of smaller things like carpet and upholstery. Once it goes back to the cathedral and starts to actually be used, then it’s more of an adjustment, rather than a big panic of “Oh my God, what are you doing?”
SN: How does it feel to finally reopen Notre Dame?
Katz: It really reminds me of the first time we went in, which I think was two months after the fire, so very soon, just as they were starting to secure the netting and really [doing] some cleaning. And I think there were all 10 of us in Notre Dame at the time, and the solitude, the stillness, the darkness, and the smell of the fire were still omnipresent.
And now to see the pictures of the interior where everything is bright and clean and pristine and all the details they’ve added, it’s really amazing, I can’t wait to be able to go inside.
An animated film by Katz and colleagues celebrating the history of Notre Dame’s acoustics premieres Jan. 24 as part of the UNESCO Voice week. In the film titled arched harmonies, music from different historical periods is reproduced as it would have sounded in the cathedral of that era.
Katz and colleagues’ audio guide, Whispers of Notre-Dameavailable on iOS and Android devices, takes listeners outside of Notre Dame, recounting the sounds of the cathedral’s past.
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