Ambisonics

Ambisonics is a series of techniques to record and replay a sound field. By means of encoding and decoding sound information on a number of channels, a 2- or 3-dimensional sound field can be presented. Ambisonic was mainly developed by Michael Gerzon and Peter Fellgett in the early 1970s.
   In contrast to more common playback systems such as stereo or Dolby surround, ambisonics  tries to resynthesize the represented sound field mathematically correct. Therefore sounds arriving from all directions are treated equally. All speakers are generally used to localise a sound in any directions. As a result the number of speakers is flexible. This portability of the format makes it easy to adapt an ambisonics-encoded signal to different loudspeaker settings. The elevation level can be decoded for any loudspeaker position. Thus a three-dimensional sound field is already presented with four loudspeaker channels. Conventional formats are even with 6 channels only be able to present a two dimensional sound field.