Zero Sound Horror
Beginning on August 1st, 2002, Zero Sound Horror was a series of short audio "episodes" continuing Miku's story after the events of Fatal Frame. It was only available in Japan, for people with DDI Pocket-brand cellphones. Users would pay a small fee and receive messages in their voicemail inbox every two weeks. The episodes were written by Tecmo staff, and used technology intended to reproduce 3D acoustic fields. Each cost 200 yen and was about five minutes long.[1] There is no detailed information available about the format or events of the story, or even how many episodes were made.
Links
Official site (Japanese)