Collect field recordings either by making them yourself or from archival resources or both. Using an audio editor, make a collage-montage. Through recorded voice or written notes, offer a framework that invites the walker to read the audio in terms of the visible landscape, and the landscape in terms of the audio.
Here are a few archives of Creative Commons field recordings:
https://commons.wikimedia.org/wiki/Category:Field_recording
https://freemusicarchive.org/search?adv=1&quicksearch=field%20recording&&
https://archive.org/details/audio?and%5B%5D=field+recording&sin=