Our hearing tells us of a car approaching from behind, unseen, or a bird in a distant forest. Everything vibrates, and sound passes through and around us all the time. Sound is a critical environmental signifier.
Increasingly, we are learning that humans and animals are not the only organisms that use sound to communicate. So do plants and forests. Plants detect vibrations in a frequency-selective manner, using this “hearing” sense to find water by sending out acoustic emissions and to communicate threats.
We also know that clear verbal communication is critical, but is easily degraded by extraneous sounds, otherwise known as “noise.” Noise is more than an irritant: It also threatens our health. Average city sounds levels of 60 decibels have been shown to increase blood pressure and heart rate and induce stress, with sustained higher amplitudes causing cumulative hearing loss. If this is true for humans, then it might also be true for animals and even plants.
Conservation research puts a heavy emphasis on sight – think of the inspiring vista, or the rare species caught on film with camera traps – but sound is also a critical element of natural systems. I study digital sound and interactive media and co-direct Arizona State University’s Acoustic Ecology Lab. We use sound to advance environmental awareness and stewardship, and provide critical tools for deeper consideration of sound in nature preserves, urban and industrial design.
Arizona State University professor Garth Paine explains the power of listening as a way to experience the natural world.
Sound as a sign of environmental change
Sound is a powerful indicator of environmental degradation and an effective tool for developing more sustainable ecosystems. We often hear changes in the environment, such as shifts in bird calls, before we see them. The United Nations Educational, Scientific and Cultural Organization (UNESCO) has recently formed a sound charter to promote awareness of sound as a critical signifier in environmental health and urban planning.
I have spent decades making field recordings in which I create a setup before dawn or dusk, then lie on the ground listening for several uninterrupted hours. These projects have taught me how the density of the air changes as the sun rises or sets, how animal behavior shifts as a result, and how all of these things are intricately linked.
For example, sound travels further through denser material, such as cold air, than through warm summer air. Other factors, such as changes in a forest’s foliage density from spring to fall, also change a site’s reverberation characteristics. Exploring these qualities has led me to think about how perceptual measures of sound inform our understanding of environmental health, opening a new angle of inquiry around psychoacoustic properties of environmental sound.
Coyotes in Usery Mountain Regional Park, Arizona. Garth Paine
Altering sound environments affects survival
To engage the public and scientific communities in this research, the Acoustic Ecology Lab embarked in 2014 on a large-scale, crowd-sourced project teaching listening skills and sound recording techniques to communities adjacent to national parks and national monuments in the southwestern United States. After completing a listening and field recording workshop, community members volunteer to record at fixed locations in the parks every month, building a large collection of sound captures that is both a joy to listen to and a rich source of data for scientific analysis.