Tuning into the Universe

The Audio Universe, led by UK astrophysicists Chris Harrison and James Trayford, is a team working to develop ways of representing astronomical data through sound. Using this process, called sonification, Chris and James have created resources and shows for accessible outreach, alongside new tools for data analysis in scientific research.

“I've always been interested in making science for everyone,” Chris says. The first spark of what would become the Audio Universe came soon after meeting Nicolas Bonne. Nic is a visually impaired astronomer, whose own work creating 3D printed astronomical models is discussed in the first part of this blog series.

Coming from a musical background, Chris’s thoughts went straight to combining astronomy with the medium of sound. For the 2019 British Science Festival, he worked with Nic to create a show that presented astronomy in a multi-sensory way. By combining a sonic tour of the Universe with Nic’s tactile models, they successfully created an accessible experience for visually impaired audiences and set the ball rolling for the Audio Universe as it is today.

The team took the lessons learnt in this pilot experience, and worked with focus groups of students and teachers to develop a full-dome planetarium show. The excerpt below demonstrates how much information can be packed into a single piece of sonified data. In this clip you can listen to stars as they appear above ESO’s Paranal Observatory in Chile, represented by notes on a glockenspiel. The brightest stars pop up first, and the pitch of the note tells you about their colour –– red stars are pitched lower, blue stars are higher. In stereo sound, notes are even played through the left and right speakers according to a star’s location in the sky. The experience is even more immersive in a planetarium equipped with a surround system. All of this works together to build a comprehensive image of Paranal’s starry sky in a listener's mind.

Since this first demonstration, the Audio Universe has continued to produce a wide range of sonifications for outreach and communication, explaining concepts like the motions of planets, the warming of Earth’s climate, and even gravitational waves.

According to Chris, the team have received feedback from visually impaired audience members saying these resources have let them connect with space for the first time. But he also emphasises that sighted audiences have found a deeper understanding of astronomy within their sonifications too. This is hugely important for Chris and James, as they see sonification’s potential as a tool for everyone to use, and want to ensure it isn’t ‘boxed in’ as a tool for a specific group of people. As Chris says, “if we want this to be really used to promote accessibility, we can't focus on just one group — we have to make this a mainstream method.”

In space, no one can hear your data

In addition to making astronomy more accessible to all, sonification can also help researchers themselves interpret their data. Chris and James have produced a Python package called STRAUSS — their so-called “sonification engine” — which any educator, communicator or scientist can use to make their own sonifications. Python is a very common coding language, which allows the user to download ‘packages’ of code that bring with them new built-in abilities. While some widely used packages allow scientists to plot their data, James asks, “why can't we have a package that will let them listen to their data?”

In astronomical research, one key benefit to sonification is the much wider range of wavelengths that we can hear, when compared to what we can see. “Our visual band is quite narrow,” James says, “it's from about 400 nanometers to about 800 nanometers. You can think of that as an octave in musical terms. That's one doubling, whereas you can hear about ten of those [doublings].”

Another useful trait is the amazing high-fidelity inherent in sound, especially when compared to visuals. As James says, “there's a reason why [we] have to sample sound like 48 000 times a second, whereas a video only needs like 30 frames a second.”

A common astronomical tool that sonification is well suited to explore is the field of 3D spectroscopy, in which telescopes capture an entire spectrum of light at every pixel in an image. James describes how this creates 3D ‘cubes’ of data, built by combining ‘slices’ of information that have been captured at different wavelengths, or colours, along the light spectrum.

“A camera with R [red] G [green] and B [blue] has maybe 2 dimensions and then three slices: the R, the G and the B,” he says, “but this [spectroscopic data] has like 1000 slices… so how do I deal with this?” He and Chris believe sonification is a possible solution, since they’ve found that spectral data can be very easily translated into sound waves.

When you listen to this data, James says there are “certain frequencies from different elements that you can listen for, and because of the speed at which we hear, you can very quickly hear and pick out where these things are popping up.” This makes sonifications excellent for finding hidden signals embedded in noisy data, as he adds that in their test groups, audiences have been able to discover new things entirely through the sound — phenomena like material flowing out of a galaxy, or catching astronomical objects as they appear. For instance, the video below shows a sonification of a galaxy observed with the MUSE instrument on ESO’s Very Large Telescope (VLT). One can hear how the galaxy is rotating by hearing changes in pitch, and how chaotic the gas is by hearing how "windy" the sound is.

Looking to the future of the Audio Universe’s work, Chris hopes that efforts like this will lead to a more inclusive environment in astronomy, but he reminds us that this “isn’t just about accessibility.”

“We want to demonstrate that everyone can get value in this. From education and immersive experiences, all the way to data analysis, sonification can benefit everyone and it increases accessibility on the way.”

Whispers of ESO’s observatories

While the sonification of data may not be widespread in its use at ESO yet, there is an ongoing project using sound to fill our archives with more accessible material. These are our soundscapes — audio tours of the telescopes located at Paranal and La Silla in Chile, pioneered by Sofia Otero, ESO Outreach Officer.

“I wanted people who could not experience visiting the observatory [to] have a more full experience about what it was,” Sofia says.”I thought the images and the videos convey something, but sound gives a very… organic feeling to it.” She found that people appreciated these soundscapes as a tool for accessibility, “but it didn't start like that. It started more like… how can we show what we are in a broader way?”

These audio tours capture details that can’t be replicated in visuals alone, particularly the differences in how the two sites feel. “La Silla is an historical place… [the instruments] are old and they crack when they move. That is something that you don't get from the picture,” she says, while “Paranal is very smooth and you almost don't hear it.”

However, according to Sofia the inside of the Paranal observatory is bursting with unique noises. Astronomers and engineers “have a different sound for every little different thing that happens on the telescope and the instruments,” Sofia says — many of which they’ve ‘borrowed’ from movies and TV.

Despite hosting a telescope full of movie references, Sofia says that throughout ESO’s observatories “the main sound is silence… but when silence is interrupted by something, it's always something special.” Without the soundscapes, these experiences would only be available to the people who work there, or are fortunate enough to visit the sites. Therefore, Sofia says that “it's accessibility in a very broad sense,” but she also acknowledges how her soundscapes provide a specific window to ESO’s work for the visually impaired.

Alongside this project, Sofia was also a driving force behind the Alt-Text attached to many of the images in ESO’s archive. This is an essential component of creating more accessible outreach, as Alt-Text is used in screen readers and audio descriptions of images for the visually impaired. Sofia finds writing these a fascinating exercise, saying they “push you to a limit where you have to be more frontal, more simple, more descriptive.”

“We still don't have a lot of alt texts in our gallery, because our gallery is so massive,” she explains, adding that it’s “impressive, but it's very focused on the images and the videos.” These are two things that Sofia hopes to change over time, especially by growing the amount of soundscapes available through community engagement. Also, to be truly engaging alt text should properly convey the beauty of these images rather than merely describe them.

Especially after talking to other people creating material for a visually impaired audience at ESO (like Amelia Bayo, who we met in part 1 of this blog series), Sofia believes that it’s important to broaden the accessibility of ESO’s communications. Not only will this benefit astronomers and enthusiasts with a range of disabilities, she hopes that these tools will help us all.

Just like Chris and James, she believes more mainstream use of tools like these will push the field of astronomy to become more accessible in the long run. “[These projects] start because there’s a special community that might need them to be more inclusive, but in the end it's something that is [useful] for everyone… I think if we spread that feeling, then we'll have more people asking for it and then we'll have more availability of these kinds of features,” she says.