This term has been covered by the website Wikipedia as "Soundwalk"
This mediawiki site, a `wiki dictionary` about the nature and practice of free improvisation declines to duplicate the content of that listing. Below there is an introduction - a simple copy and paste. from Wikipedia then a link to the Wikipedia entry.
Introduction, copied from Wikipedia
A soundwalk is a walk with a focus on listening to the environment. The term was first used by members of the World Soundscape Project under the leadership of composer R. Murray Schafer in Vancouver in the 1970s. Hildegard Westerkamp, from the same group of artists, defines soundwalking as "... any excursion whose main purpose is listening to the environment. It is exposing our ears to every sound around us no matter where we are." 
Link to the Wikipedia page