Brian F.G. Katz

From Notre-Dame to concert halls and virtual reality, Brian F.G. Katz has spent more than 20 years unraveling the mysteries of sound. A CNRS research director at the Institut Jean le Rond d’Alembert, he seamlessly bridges the past and the future, combining fundamental research with practical applications. This is the story of a physicist who has mastered echoes.

“It was too good to be true.” Brian Katz vividly recalls the moment a colleague told him about Penn State, one of the few universities in the world offering a degree in acoustics. For this American student, more drawn to sound systems than astrophysics or quantum physics, it was a revelation.

After earning a bachelor’s degree in physics and the philosophy of religion in the United States and a master’s in materials science in England, Katz pursued a PhD at Penn State. His research focused on active noise control in airplanes and modeling sound around the human head using supercomputers.

From Concert Halls to Research

After completing his PhD, Katz became one of the first researchers to model the acoustic impact of the human outer ear. He then worked as a consultant for renowned U.S. firms specializing in the design of concert hall acoustics. “It was extraordinary to work on concert halls I’d only ever seen on TV,” he recalls.

At the same time, Katz pursued his passion for research. “If I finished a project for the firm ahead of schedule, I could use the rest of the time for research. I did this for a few years, but eventually, I was working 80 hours a week,” he says. Forced to make a choice, he decided to prioritize research.

A Leap into French Academia

A Chateaubriand fellowship gave Katz the opportunity to explore research in France at the Laboratoire d’Acoustique Musicale (LAM) at the Université Pierre et Marie Curie. “My boss offered me a one-year leave of absence. If it didn’t work out, I could return to my job in the U.S.,” he recalls.

But Katz isn’t one to back down. After a few months, he decided to stay in France. “It was a definitive choice, even though I didn’t have a guaranteed position. I loved academic life,” he says. Fortune smiled on him when a researcher at IRCAM left a position open. “I was lucky to pass the CNRS recruitment process on my first attempt,” he notes with gratitude. At 31, Katz became a permanent researcher, spending eight months at IRCAM before joining LIMSI on the Saclay plateau. There, he spent 15 years developing research on sound spatialization and virtual auditory reality.

Balancing Fundamental and Applied Research

“My research sits at the intersection of practical applications and fundamental studies,” explains Katz, who alternates between academic collaborations and industrial projects. Since joining LAM in 2017, Katz has continued consulting for international firms, including his former employers. “Even though I have less direct contact with clients, I’m exploring new methods,” he says.

For example, he refined acoustic measurement techniques for concert halls. “We developed a scaled-down model system to test and optimize configurations. This method was particularly effective in the design of the Philharmonie de Paris,” he adds.

Over the years, Katz has contributed to prestigious international projects, including the KKL Luzern, the renovation of the Mogador Theatre, an opera house in Suzhou, China, and improving the acoustics of the Louvre Pyramid. “We conduct virtual simulations to test and present solutions to the museum, such as adding suspended sculptures to enhance the acoustics in this highly trafficked space,” he explains.

Reviving Lost Acoustics

Katz’s expertise extends to historical sites whose acoustics have disappeared. “The techniques we use to predict the acoustics of new buildings are the same ones we apply to study past acoustics,” he explains. His work includes virtual reconstructions of the acoustics of the Théâtre de l’Athénée and the Palais du Trocadéro.

Breathing New Life into Notre-Dame

The Notre-Dame de Paris project marked a significant milestone in Katz’s career. In 2015, his team conducted acoustic measurements of the cathedral to create a virtual model of its soundscape. This work became invaluable after the 2019 fire. “We were the only team in the world with modern acoustic measurements of Notre-Dame,” he emphasizes.

Katz initiated a major research project on the historical evolution of the cathedral’s acoustics, collaborating with a multidisciplinary team of architects, historians, acousticians, and musicologists. “I love working with people from different fields,” he says.

His team developed a real-time acoustic simulation system, enabling singers to perform within a virtual Notre-Dame. “We can adjust the acoustics to reflect different historical periods and analyze performers’ experiences,” he says with excitement. “We are likely the first to develop such an advanced system calibrated for multiple singers simultaneously.”

Katz also monitors how the fire and subsequent restoration have impacted Notre-Dame’s acoustics. “Cleaning and polishing the plasters affect the sound. We’re tracking the renovations and conducting regular measurements. We hope to continue collaborating on the scientific aspects of the restoration once the work is complete, particularly to help select interior acoustic features for the cathedral,” he explains.

“For instance, minimizing public noise is essential so it doesn’t disrupt prayers. During our research, we analyzed medieval decorative elements, such as velvet curtains and tapestries, to measure their acoustic properties. We believe it’s possible to reintroduce some of these to improve acoustics while respecting the historical aesthetics. The idea of bare church walls is actually quite modern. During Napoleon’s coronation, for example, the cathedral’s walls and columns were covered with drapes and tapestries,” Katz notes.

Through his work, Brian F.G. Katz demonstrates how science can honor both history and innovation, crafting spaces that resonate with the past while inspiring the future.