In the flat lands of California’s Central Valley, oil pumps obscured by waving lines of fuel-richened air dip and rise on the horizon. Two hundred miles to the north and west, aging eighteen-wheelers pound through an urban bypass tunnel, staining the walls black with diesel fumes. Farther to the north, High Sierra pines scent the mountain air with notes of cinnamon and nutmeg, sending blue wisps of haze trailing gently upward.
Air is not the same everywhere. Across the extremes of the human environment, in both urban areas and wild, powerful natural and human forces combine to create intricate mixtures of chemicals that compose the air we breathe, seek for pleasure, or avoid. And now that air is made audible.
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.