Audio Astronomy Unlocks a Universe of Sound

“Growing up, I would get people asking, ‘How in the world are you going to be an astronomer? If you can’t see through telescopes, you can’t see the stars,’” Kane says. “But that’s not really how modern astronomy works. A lot of the time astronomers are just doing data analysis on computers. Computers can be made accessible.”

To realize their dreams, Kane and other budding blind or visually impaired (BVI) researchers are betting big on efforts to turn scientific data into sound, also called sonification. At a conference at the Lorentz Center in the Netherlands last December, a motley crew of scientists, sound engineers and educators representing the leaders of the nascent field of astronomical sonification gathered to discuss current projects and chart a course forward. Their work is poised to expand accessibility for future generations of BVI scientists and to create new ways for all astronomers, sighted and BVI alike, to analyze the cosmos.

“The more blind people you have in astronomy, the more voices like mine calling for these changes and improvements, the more we’ll see a snowball effect,” Kane says.

She experienced her first astronomical sonification during the early phase of the COVID pandemic, when she advised a project called Astronify. Researchers played Kane a variety of chimelike tones to determine her preference for which pitches and timbres best captured a planetary transit—when a star’s light dims because of an accompanying planet crossing its face, as seen from Earth. She likened the sound of this brief passage to a quick, abbreviated glissando on a piano. Overall, Kane found the experience quite intuitive.

“We are used to thinking that astronomy is a visual science, but that’s actually just a habit that we have,” says Anita Zanella, an astronomer at the Italian National Institute for Astrophysics and one of the organizers of the December conference. “We are basically all blind to the sky; we can see just a tiny fraction of what’s up there. And the rest is just a representation that we give.”

Astronomical sonification has mostly been used for educational purposes, as a tool to inspire BVI individuals, much as vivid pictures of galaxies from the world’s greatest telescopes have inspired sighted people for generations.

The conference, Zanella says, was an early step in a greater journey toward standardizing and expanding the field. Like many largely grassroots efforts, astronomical sonification lacks any central organizational structure to formally track all the various initiatives. One of the conference’s key tasks was to take stock of the 100 or so existing projects to determine just how much activity is occurring. From there, the grander goal of developing a framework for sonifying data in both educational and research contexts could be within reach.

There is no shortage of work to be done. Currently, researchers lack agreement on even the most basic questions: Should they use a low pitch or a high pitch to represent a very bright star? Are listeners more receptive to sounds from real musical instruments or those from computer synthesizers? Can sonification even be a useful tool for serious astronomical research?

“Standardization is hard! There’s no handbook saying, ‘You want to sonify data? Start here,’” says Kimberly Arcand, a science communicator who sonifies data from NASA’s Chandra X-ray Observatory.

In Search of Standards

Sonification is not exactly a new scientific concept or tool. Consider the ominous clicking of a Geiger counter, a device invented in 1908 that uses sound to track radiation levels. Astronomical sonification, too, has existed in various forms for decades. For instance, think of the metronomelike ticking of a whirling pulsar as heard through a radio telescope or, more recently, of the “chirp” that in 2015 signaled the first-ever direct detection of gravitational waves from a merging pair of black holes. What is new, however, is astronomers’ increasing awareness of and sensitivity to the needs of BVI researchers and layfolk.

Beyond issues of accessibility, using sound rather than sight for scientific analysis has its advantages. Human ears can register changes that are invisible to the eyes, and our ears are more adept at filtering out noise. This doesn’t mean that creating audio that inspires students or aids astronomical research is straightforward, however. When British astronomer Chris Harrison created an audiovisual show to take BVI kids in classrooms in Newcastle, England, on a tour of the solar system, he used “cool spacey sounds” to represent the solar system, he says. It flopped.

“We played them to some kids, who said, ‘I have no idea what this is. It’s rubbish.’ They were like, ‘Can’t you just use musical instruments?’” says Harrison, who is a Newcastle University Academic Track Fellow at the university. “So we did, and that was much preferred. It’s really clear to us that you need that dialogue.”

After its initial flop, the now revamped show achieved success with a mix of visuals, narration and sonification to render the solar system. As the planets and the sun orbit listeners’ and viewers’ “head,” each heavenly body emerges with a distinct pitch and instrument that corresponds with their motions—for example, Jupiter features a rumbling bass trombone.

Harrison plans to use the open-source code he created for the show as a template for other sonifications. He says the show’s feedback will inform a potential framework.

“We have bar charts; we have scatter plots; we have pie charts. We have this standard set of figures that you learn all the way through school and university, but there’s still customization within them,” he says. “I think that’s our goal: to create a standard framework of, like, ‘this is how you do the sound mapping.’ But within that, you can make some personal choices.”

Making customizable tools that can adapt to a listener’s cultural background is crucial for educators and scientists, says Rubén García-Benito, an astrophysicist at the Institute of Astrophysics of Andalusia. He uses the experience of two of his musician colleagues as an example: One was trained in European classical music, whereas the other worked in Persian traditional music. Each musician initially found the other’s regional music boring but learned to appreciate it after extensive listening.

Astronomical sonifications operate similarly, García-Benito says. Western audiences would likely experience a learning curve with sonifications that employ, say, the sound of a Javanese gamelan, but a framework that contains such options can flex and adapt to the data’s needs.

“We all live under the same sky,” he says. “If the universe is silent, it would be important that the cultural background that we imprint in the sonification for astronomy is plural, so it has many voices.”

A Clarion Call

As the self-described “den mother and grand secretary” of the field, Kate Meredith has spent years organizing online panels about sonification and lobbying for more funding for research.

“It’s much easier to say, ‘I need a wheelchair-accessible telescope building,’” says Meredith, who is president of Geneva Lake Astrophysics and STEAM (GLAS), a group dedicated to creating inclusive scientific practices. “But because [astronomical] sonification is so new, because it’s not well understood, getting those first ‘yes’s’ is a challenge.”

Existing sonification projects might help secure funding and serve as proof of scientific utility. Because human ears excel at perceiving patterns, many sound-savvy astronomers are taking noisy data sets and using audio cues to sift through the trash. Zanella’s forthcoming work will sharpen our perceptions of far-away galaxies. Besides sonifying exoplanet transits, researchers are experimenting with audible data for supernovae and other transient cosmic events.

Pitch is often used as the variable to represent data because humans remember pitch relationships better than loudness or timbre. Meredith is optimistic about the future of astronomical sonification, but she says other guidelines must emerge to allow the practice to broaden its current pedagogical focus and become a robust analytic tool.

“Until you get enough research published, standardization isn’t going to emerge,” she says. “You don’t just go and invent a standard. You test and explore, and standards emerge from those experiences.”

As a legally blind young astronomer, Sarah Kane is uniquely poised to take advantage of these new technologies. “I’m quite optimistic about [sonification’s] potential. I’m not as optimistic about the timeline,” she says. “Grant money moves science. But I don’t think that slowness is indicative of the potential of sonification.”

That potential will be on display later this year when Zanella and her colleagues transform the Italian village of Castellaro Lagusello for an astronomical sonification festival, with talks and demonstrations for thousands of BVI individuals. She believes events like these can inspire the next generation of scientists.

“I think there is a very strong link between being human and wondering about astronomy, what’s in the sky and how things are related,” she says. “And there are so many incredible things up in the sky. I think everyone should have access to that beauty.”