Immersive audio technologies
Entry compiled by: Jeffrey A. Haines
There are basically two fields of thought on the immersive audio aspect of virtual reality.
With surround speaker systems, the audio experience depends less on the amount of speakers, than the shape, size, and construction of the room. The distance of the speaker from the audience member's ears, as well as the spatial position and rotation of speaker relative to the listener, as well as the aforementioned listening environment factors determine the extent to which "reality" is created. This type of immersive sound works best in group settings, where the atmosphere of a group experience needs to be preserved--some people go to the movie theater just to experience the film with others. Currently, the standard for surround sound is5.1 Stereo Surround Sound, but looking ahead, immersion technologies may use a 22.2 system.
Holophonics relies on just two speakers, as humans only have two ears, and therefore if one speaker is allocated to each ear, all human experiences can theoretically be recreated through manipulation of the audio waves. Close proximity speakers (headphones) are the only real way for this technology to work, although workarounds have been developed for speakers. Holphonics is limited to a single user experience, unless each user has a separate set of headphones, and even then, for them to have the same experience, the sound would have to be adjusted relative to their position to create a multi-user invironment. I was able to locate this great resource for holophonic sound information: Holophonic Sound: 3d audio with just two speakers.
Stereo Immersive audio
Entry compiled by: Steve Benjamin
Here is an example of holophonic sound that I was able to locate. If you listen to the audio file through headphones, you will get a sense of immersion in a virtual environment.
This .pdf file of a book by NASA describes the technical principles of audio and its relation to and applications in VR.