In the late 80s, researchers at Delft University of Technology, Holland, set out to adapt Huygens’ theory to sound waves. The potential of wave field synthesis in audio engineering was further explored by a consortium of eight European institutes in the late 90s and finally brought to fruition by a group of researchers at Fraunhofer IDMT working under the leadership of Karlheinz Brandenburg.
wave field synthesis
At the core of IOSONO® spatial sound technology lies the principle of wave field synthesis. It is based on a theory developed by seventeenth-century physicist Christiaan Huygens, who stated that the wave front of light can be regarded as a superposition of numerous smaller waves. The smaller waves emanate from points in space through which the original wave front passed at an earlier moment.
synthesizing wave fronts
In practice, the smaller waves required to synthesize the desired wave front are produced by a large number of loudspeakers fixed at equidistant positions along the perimeter of the listening space.
A computer controls each loudspeaker separately and actuates it the moment the desired wave front would pass through it. To synthesize a spherical wave front originating from a point behind the speakers, for example, the speaker closest to the virtual source is actuated first, followed by the speakers to the right and left of it. This results in a wave front with a relatively large radius and a virtual source point outside of the listening space. Reversing the order of actuation (where the speakers closest to the virtual point source are actuated last) results in a wave field corresponding to that of a source within the listening space.
The result is a stable wave field in which the listener can localize the virtual sound sources as if they were emanating from actual objects. The loudspeakers themselves, however, cannot be localized. Wave field synthesis thus creates a stunning illusion of acoustic events in a space, adding a whole new dimension to audio in the entertainment and other industries.
