Surround sound

Source: Wikipedia. Pages: 41. Chapters: 10.2 surround sound, 22.2 surround sound, 5.1 surround sound, 7.1 surround sound, Ambiophonics, Ambisonics, Ambisonic decoding, Ambisonic UHJ format, Center channel, Dolby Atmos, Dolby Digital, Dolby Pro Logic, Dolby Surround 7.1, DTS (sound system), Height channels, MP3 Surround, Quadraphonic sound, Sony Dynamic Digital Sound, Surround channels, Virtual surround. Excerpt: Ambisonics is a series of recording and replay techniques using multichannel mixing technology that can be used live or in the studio. By encoding and decoding sound information on a number of channels, a 2-dimensional ("planar", or horizontal-only) or 3-dimensional ("periphonic", or full-sphere) sound field can be presented. Ambisonics was invented by Michael Gerzon of the Mathematical Institute, Oxford, who ¿ with Professor Peter Fellgett of the University of Reading, David Brown, John Wright and John Hayes of the now defunct IMF Electronics, and building on the work of other researchers ¿ developed the theoretical and practical aspects of the system in the early 1970s. Ambisonics offers a number of advantages over other surround sound systems: Ambisonics also suffers from some disadvantages: In the basic version, known as first-order Ambisonics, sound information is encoded into four channels: W, X, Y and Z. This is called Ambisonic B-format. The W channel is the non-directional mono component of the signal, corresponding to the output of an omnidirectional microphone. The X, Y and Z channels are the directional components in three dimensions. They correspond to the outputs of three figure-of-eight microphones, facing forward, to the left, and upward respectively. (Note that the fact that B-format channels are analogous to microphone configurations does not mean that Ambisonic recordings can only be made with coincident microphone arrays.) The B-format signals are based on a spherical harmonic decomposition of the soundfield and correspond to the sound pressure (W), and the three components of the pressure gradient (X, Y, and Z) (not to be confused with the related particle velocity) at a point in space. Together, these approximate the sound field on a sphere around the microphone; formally the first-order truncation of the multipole expansion. This is called "first-order" because W (the mono signal) is the zero-order information, corresponding to a sphere (const