Kind: captions
Language: en
France's Notream Cathedral has endured
for more than 850 years through the
Middle Ages, the French Revolution, and
two world wars. It's played roles in
history, literature, architecture, and
even a Disney movie. But along with all
that, [music] one of the things that
makes this place so unique is its sound.
From its bell towers to its massive pipe
organ to the echo of every footstep
[music] and whisper inside the building,
Notradam has long been known for the
[music] way sound moves within its
space. [bell]
So, a lot was [music] at stake when a
fire broke out in 2019. And without the
work of hundreds of architects, [music]
engineers, builders, and physicists,
much of Notradam's iconic sound may have
been lost to history.
Notradam sound is unique because, well,
sound in every space is unique.
Acoustics is a science that deals
specifically with the physics of sound,
but acoustics can also refer to things
[music] like the materials and
structures that make up a building.
Things like wood, stone, carpet, the
shape of the ceiling, and the position
of benches or columns can all shape the
way things sound. And even small changes
to these materials and structures
[music]
can change the way things sound in that
space. Sound travels to the air in
[music] waves. When you do something
like strum a guitar or hit a drum, it
makes a [music] vibration. And that
vibration makes the air molecules around
the instrument vibrate. [music]
And as those molecules vibrate, they
bump into more molecules and make them
vibrate and on [music] and on, creating
what's known as a longitudinal
soundwave, which allows sound to travel
[music] from the instrument to your ear.
Along the way, these waves can interact
with the materials and structure of a
space. They might bounce off hard
surfaces like [music] stone or be
absorbed by softer surfaces like carpet.
In a small space, it doesn't take long
for sound to bounce off the walls and
back to your ears. But in a larger
space, there are a lot more places for
the sound to go. [music] So, one way to
measure acoustics is to measure
reverberation time, or how long it takes
before we [music] can no longer hear
reflected sound in a space. We measure
that [music] by seeing how long it takes
a specific sound, known as an impulse
source, to fade [music] away. And in
Notream, with its high ceilings, marble
floors, plenty of wood and limestone,
[music] plus some iron and lead.
Remember, it was the Middle Ages.
There's lots of space for sound waves to
[music] move through and lots of stuff
for them to bounce off of without being
absorbed. On average, sound hangs around
in Notradam's air for 6 seconds. We know
that because of Dr. [music] Brian Katz,
an expert in acoustics who has spent
more than a decade studying Notream
sound. [music] Katz published a series
of acoustic measurements taken
throughout the cathedral. Before his
work, there was very little consistent
or reliable data documenting [music] the
building's acoustics. So, Katz's team
placed specialized equipment throughout
the cathedral, including 12-sided
loudspeakers [music] and omniirectional
microphones to capture and measure
differences in sound [music] in
different parts of the building. Then,
they conducted a series of tests to
measure reverb in the cathedral.
Different pitches produce sound waves
that may be closer [music] or farther
apart and can move around a space in
different ways. So they used the swept
sign method, [music] sending out audio
signals at different frequencies using
loudspeakers and recording the
reverberation with microphones. [music]
They also did balloon bursts, literally
popping a balloon
in different spots around the cathedral
and measuring the sound. Catz used all
his data to create digital models of
Notradam that could simulate how music
would sound in different parts of the
cathedral and what would change if
Notredam's materials or structures were
different. Which brings us back to
[music] 2019 when things in Notream
changed a lot. Shortly after the fire,
French President Emanuel Macron
announced that Notradam would be
completely restored. [music] And since
cats was the only one who had
measurements of the acoustics, his
research would become a crucial part of
the rebuild. In 2020, [music] as work
was underway to make the building stable
for workers to begin the restoration
project, [music] Katza's team was
allowed back into Notream to conduct
more tests. This time, it wasn't safe
just to walk in with a bunch of mics.
[music]
So, remote controlled robots pulled
equipment throughout the building. And
when they compared the 2020 numbers to
the data from 2015, the results were
pretty stark. Notredam was 20% [music]
less reverberant than it had been before
the fire. Cats used the data and models
to consult with those [music] working on
the rebuild and show how the sound would
change if they did things like adding
more glass to the structure. One
proposal suggested moving the organ to a
different location that would be more
visible. But the digital model suggested
the organ sound couldn't [music] carry
throughout the building as well, so they
left the organ where it was. In December
2024, Notredam reopened to the public.
Soon after, Catz [music] and his team
began the work to take new measurements
of the space. Even before analysis of
the data was complete, cats expected
[music] that the cathedral might be even
more reverberant than it was before the
fire. That's partly [music] because the
organ pipes and limestone were cleaned
and the carpet that was installed in the
1980s was removed, leaving more exposed
marble. For a place like Notradam, no
one expects things [music] to remain
unchanged for more than 850 years. But
thanks to Katz's [music] work, we now
have a clearer sense of how the
cathedral once sounded, a fuller
appreciation [music] of its acoustics
today, and the knowledge to preserve
this living history [music] of art,
architecture, and reverberant sound for
generations to come.