Throughout the world, there are an estimated 370 million indigenous people and they speak a majority of the world’s approximately 7,000 languages, according to the United Nations (UN).

The UN, however, notes that because only about 3 percent of the world’s population speaks 96 percent of the languages, many are in danger of disappearing forever.“These are languages that are spoken by only a handful of elders and are not being acquired by children and, as the remaining native speakers die, one by one, the languages are dying with them,” the UN’s 2009 State of the World’s Indigenous Peoples report notes. “In fact, it has been estimated that roughly 90 percent of all existing languages may become extinct within the next 100 years.”

But researchers at the University of California, Berkeley are doing what they can to preserve rare audio recordings of 78 of the Golden State’s indigenous languages.

The audio, found on approximately 2,700 wax cylinders from the Phoebe A. Hearst Museum of Anthropology’s collection, was recorded in the early 20th Century by anthropologist Alfred Kroeber, who was the founder of the UC Berkeley Anthropology Department.

According to a Library of Congress lecture given by Olivia Dill, who is working on this project, Kroeber and his students collected these recordings as part of a survey on ethnic California cultures.

In the 80s, many of these recordings were transferred to reel-to-reel tape, but this did not include any of the damaged cylinders and the sound quality made the content difficult to understand.

Because these wax cylinders are fragile, researchers are now using a non-invasive optical scanning technique developed by physicists Carl Haber and Earl Cornell, according to the National Science Foundation.

Traditionally, a modern stylus and cartridge would be used to play the wax cylinders like a phonograph record, Haber explained in an email interview.

“The technology we use is optical and therefore makes no mechanical contact to the surface,” Haber said. “We add no possible damage and can play cylinders which are delicate, damaged, broken or otherwise unplayable by the traditional means.”

Researchers used a scanning machine, dubbed IRENE (Image, Reconstruct, Erase Noise, Etc.), to capture audio information through 3D imaging of the cylinder’s grooved surface, according to the Library of Congress.

“We use a 3D microscope, called a confocal microscope, to measure the shape of the groove on a large number of points,” Haber explained. “With many tens of millions of measurements, we create a 3D digital map of the entire surface.”

From there, Haber said they use an algorithm to read the digital map and “calculate the trajectory of a virtual stylus.”

“We then use the physics of the sound recording process to calculate the sound corresponding the motion of this virtual stylus,” Haber explained.

The technique was also used to make inventor Alexander Graham Bell’s voice audible for the 2015 “Hear My Voice” exhibit at the National Museum of American History.

University of California, Berkeley linguist Andrew Garrett, who has also been working on this project, told Circa that this technique even allowed researchers to extract sound from broken cylinders.

“As long as you can figure out how they go together, you can extract the sound out of the broken cylinder and these have never been played before,” Garrett explained.

Garrett added that because these recordings include a range of songs and stories, they are especially significant and helpful for communities interested in language revival.

“There also are a lot of kinds of texts and kinds of speech styles that are only represented here,” Garrett said. “In some parts of California, traditional oratory was very well developed and an important kind of verbal art.”

According to Garrett, the university is collaborating with people in various tribal communities to help make sure the recordings are available to them.

For about eight languages in this collection, these are the only recordings that exist.

“Every case that I know of, there is content on these recordings that is someway lost in the current community,” Garrett explained. “So people who are trying to reinstate their traditional culture and their traditional language can use all of this material to do that.”

Read more stories from Alix Hines on Circa.