Joseph's gohst is an iPhone app. It uses the Soundcloud API to load sounds based on your GPS location. Every sound in Soundcloud has geo tags. The app shows a map interface which shows the area where the sounds are positioned.
The user can start walking around in this area listening to the sounds. When the user gets closer to the exact GPS location, the sound will turn up in volume. Because the app is created for an event in winter, the user won't need to use the interface, the user can just listen to know directions to go to and compose it's own audio tour.