Aaron Rueben and Gabriel Isaacman used data from sampling air in tunnels, where there are a lot of cars, to create unique soundscapes that represent the chemicals in the area.
We created sounds from air samples (atmospheric particulate matter collected on filters) by first using gas chromatography to separate the thousands of compounds in the air (try it with markers at home) and then using mass spectrometry, which gives us a unique "spectrum" for chemicals based on their structure, to identify the compounds and assign them tones. Some compounds end up sounding clear and distinct, while others blur together into unresolvable chords. The result is a qualitative, sensory experience of hard, digital data. You can actually hear the difference between the toxic air of a truck tunnel (clogged with diesel hydrocarbons and carcinogenic particulate matter) and the fragrant air of the High Sierras.
The audio above represents the air in the Caldecott Tunnel Oakland, California. Note the heavy hydrocarbons towards the end. Contrast that with the audio for a remote forest in the Sierras below.