WFS & The Game Of Life
About Wave Field Synthesis
What is Wave Field Synthesis?
Wave Field Synthesis (WFS) is a sound production technology designed specifically for spatial audio rendering. Virtual acoustic environments are simulated and synthesised using large numbers of loudspeakers. The innovation of this technology is that sound can appear to emanate from desired virtual starting points, and then move through space in many possible defined spatial pathways. The WFS system from The Game of Life consists of 192 speakers, which are arranged in a square formation of 10 by 10 meters. Within this formation sounds can be composed to move within this square space, however the interesting point is that it is also possible to move sounds outside of this loudspeaker square. So the question is what makes this phenomenon possible considering the loudspeakers are all physically directed inwards.
The WFS technique is based on a theoretical principal of the Dutch mathematician and physicist Christiaan Huygens from the 17th century. In this principle a spherical wave passes its energy to its neighboring ‘particles’, which in turn radiates another spherical wave, in such a way that the wave at position X can be predicted. In other words, this principle states that any wave front can be regarded as a superposition of elementary spherical waves. This means that any wavefront can then be synthesised from such elementary waves.
So the WFS system synthesises wave fronts according to this principle of Huygens. The basic procedure of WFS was developed in 1988 by Professor Berkhout at the Technical University of Delft. Unlike conventional audio procedures (e.g stereo /surround) the perception of these wave fields is not dependent on psychoacoustic phantom sound source perception. The WFS sound field is actually reconstructed physically.
The positioning of sound within the stereo system (that is based on the same principal as surround) originates from intensity differences or short time differences between both speakers. In the ‘real world’ when sound is perceived from a natural sound source in the environment it arrives at one ear slightly earlier that the other (that is, if the source is not situated straight in front of the listener). Because of this inter-aural time difference we (for frequencies below 1.500 Herz) use this information to determine which physical direction the sound is coming from.
With stereo reproduction technique the sound of the left loudspeaker arrives first at the left ear and later at the right ear, and sound from the right loudspeaker arrives first at the right ear and then later to the left ear. The human brain ‘makes sense’ of this intensity difference to determine the ‘apparent location’ of the sound source.
For the perception of natural sound sources above 1.500 Herz use is made of inter-aural time differences as well as a colouration of the sound, caused amongst other factors by the physical interference of the human head and ear lobes. Again the normal stereo system is deficient in rendering this spatial information and fails to convince, because the sound comes from two loud speakers. Phantom locations emerge and the sound placement is very difficult to localise with any precision. In this situation the brain determines the apparent location of the sound based on the apparent intensity difference. The listener needs to be situated exactly in the middle of the speakers in order to correctly perceive the positioning of stereo sound, because this is the only spot where the ratios of the intensity differences are accurate. With the WFS technique by means of a large number of loud speakers the wave itself is reconstructed. This ensures that the distance between the sound source and the listener is smaller than the distance between listener and the loudspeaker, so any desired wave can be reconstructed. This possibility cannot be achieved with stereo technique, because the loudspeakers are the sources themselves and do not reconstruct a source.
Practically speaking a computer controls a large array of individual loudspeakers arranged as arrays around the listener and the computer synthesis activates each solitary loudspeaker membrane, at the time when the virtual wave front would pass through it.
Sounds are no longer simulated (like stereo and surround systems which use psychoacoustic principles to ‘fool’ the perceptual system) and sound reproduction is no longer based on psychoacoustic principles, but instead on purely physical principles.
About The Game of Life Foundation:
The Game of Life was founded on September 13, 1999.
The Game of Life aims to organize projects in the field of spatial representation in electronic music.
With our programming we bring a diversity of high quality electronic music into the limelight.
We offer composers (in the broadest sense of the word) the opportunity to work with our mobile Wave Field Synthesis playback system (the only mobile WFS system in the world). In doing so, we offer listeners an experience that cannot be enjoyed with current surround sound systems at home.
We are closely involved in the process of creation, production and programming and help venues with audience development where possible.
How it began
The foundation’s name comes from a project by Arthur Sauer that was organized by Erwin Roebroeks.
For this project, an eight-channel 3D sound system was designed and an inflatable, igloo-shaped tent was built. This made it possible to perform at a wide variety of venues. Therefore, the motto was “the stage comes to you. Because of its appearance, the mobile stage was very approachable, which led to a diverse (multicultural) audience.
The next step was to build our own, mobile WFS system.
Wave Field Synthesis (WFS)
With our special WFS system, a unique acoustic environment can be created. Because the system is mobile and flexible, it can be set up anywhere.
In 2004 we traveled with a number of composers to the Fraunhofer Institute in Ilmenau to listen to WFS. Everyone was convinced that the system worked. But we were also convinced that it could be done better and cheaper. So we decided to build a WFS system ourselves. Wouter Snoei developed the software, architect Raviv Ganchrow designed and built the speakers, and Jan Trützschler programmed the synchronization of the computers with each other. We were given access to TU Delft’s dead space, including technical assistance. After measurements by the TU, our system proved to meet all quality requirements. Because the software is open source, anyone can modify it at will. Students at the Institute of Sonology are currently programming new features for the system.
November 2006 saw the premiere of the first concert in the series “THE 192 Loudspeaker Experience (Focussed Sound in Sonic Space). Due to great public interest, concerts had to be continuously scheduled.
In the meantime, there has been much interest from composers, programmers and other institutions in working with the WFS system.
Who is the game of life ?
The Game of Life foundation currently consists of: