There was no Christmas mass at Cathedral Notre-Dame last year. On April 15, 2019, part of the Paris landmark burned down as its spire restored in the 18th century and the medieval roof structure from the 12th century caught fire. In 1803, the cathedral reopened after the French Revolution to start Christmas mass again, and the mass was suspended in 216 years due to the devastating blaze last year. With parts of the magnificent edifice gone, the beautiful tunes that once reverberated the masses were also missing.
It was in October last year that the operation began to clear the debris, and recently Notre Dame is being frequented by acousticians. Their job is to restore the sound of the place that went missing along with the debris. Science News, the American scientific magazine, reported the story of Brian Katz, a researcher at the French National Center for Scientific Research, who is restoring the acoustic grandeur of the church.
The “map of sound” that the researchers previously created by chance is playing a pivotal role in the restoration work. In 2013, the researchers recorded the sonic traits of Notre Dame by installing scores of microphones and other equipment at night. They compared this data with computer simulations to predict how the sounds travel. The unique acoustic patterns caught their attention, so the researchers drew up maps of sound based on the data. When a footstep is made in silence at Notre Dame, the sound often lingers, repeating itself for seconds. The phenomenon is called a reverberation where the soundwaves arrive with an interval after reflecting against the walls, floors, or ceilings. The longer the reverberation is, the deeper and warmer the sound tends to grow.
The sound maps will serve as data to analyze the effect that the design of the building and its building materials have on sound qualities. Researchers stressed that even minor choices such as whether to carpet some of the aisles could create a big difference in sound.