Voice Trust Walk

Follow the same procedure as a Trust Walk, only this time there is no physical contact between the leader and the follower. Blindfold the follower, lead them on a hike guiding with your voice only. You must talk constantly; never stop talking. Warn them of problems by describing them and how to overcome them. Once you have lead the follower for 10 minutes or so, swap places.

Source: From the original site.