The Implementation Of IOSONO And The Development Of Wave Field Synthesis Technology For 3-D Immersive Surround Sound In Large Cinematic Venues

28-Jul-04

The optimum sound in a movie theater can usually be experienced by only a few people in the audience. The most important disadvantage of the current surround sound systems lies in the fact, that the listener and the loudspeakers must be placed at certain positions. Outside of this determined range the quality for optimal sound cannot be provided. Other deficiencies of these surround sound systems are the lack of realistic reproduction of the position of natural and also virtual sound sources. The IOSONO system, using Wave Field Synthesis (WFS) technology, allows one to re-produce an accurate spatialization of sound and therefore a more natural sound impression for nearly all of the reproduction area. The basic idea comes from Christiaan Huygenís principle of wave propagation, in which the wave field of a source can be reproduced by many sources located on the perimeter of the original wave field. Using this principle in conjunction with audio allows the realistic emulation of virtual audio sources and audio waves as desired by means of an array of closely spaced loud-speakers. In practice, this means that the listening area is surrounded by many loudspeakers. Each of them is driven by a unique signal that depends on the position of the virtual source in space and of the speaker. As a result, the positions of the virtual sources are already specified in the system. The room reflections are then either measured or simulated and also integrated into the WFS system.In the implementation of Wave Field Synthesis, the level, position and distance of each sound source is recorded and processed separately from the acoustic characteristics of the room. With this separation, it is possible to manipulate the source characteristics and the room information in an independent manner. In contrast to other surround systems, the position and direction of the source are exactly reproduced. In addition, IOSONO allows to place virtual sources inside the room (i.e. in front of the speakers), an ability that other systems cannot offer. These characteristics open the door to new creative possibilities. To store and distribute the audio sources and their positions and characteristics, the 3D-Audio profile of the MPEG-4 standard is used. MPEG-4 is the state of the art for efficient coding of high quality object-oriented audio data and offers interactive controls on the listenerís side. Playing discrete channel recordings, such as stereo or 5.1 surround, over IOSONO drastically enlarges the optimal listening area, the so-called sweet spot. This is accomplished by placing each audio channel as virtual source at greater distance and even outside of the room. This has the benefit that the left and right channels or the front and rear are in the correct position for all of the listeners rather than only for those sitting in the center of the room. This improvement of the sweet spot also adds to a better sound impression in the entire reproduction room. The movie theater ""Lindenlichtspieleî in Ilmenau, Germany, is the worldís first theater to be outfitted with a WFS sound system. This new system is run daily with an ever increasing attendance. The theater seats 89 people and has 24 panels of all together 192 loudspeakers lining the room. The panels were developed by the Fraunhofer researchers to accept an ADAT input. Each panel has eight two way speakers and eight 50 Watt amplifiers. These panels receive their signals from Computers which are equipped with ADAT soundboards and specially developed software. The number of computers and ADAT soundboards depends on the room size. The central control unit is connected to each panel by an optical ADAT-cord and to a Dolby Digital sound processor. The integration of the Dolby processor is the determining factor for the mentioned compatibility with 5.1-channel encoded films. For the rendering of audio material produced by IOSONO, the audio inputs to the system come from media such as DVD, CD or hard-disk. The components of the movie theater system are transferable to any other WFS system and scalable in size, depending on the conditions of the room and the application.Later this year, more movie theaters and show theaters in Germany and worldwide will be equipped with the new Wave Field Synthesis-(WFS) technology. This technology is, however, in no way limited to film or theater applications. IOSONO can also be used at conference centers, planetariums, Rendering-computers with Dolby Sound Processor in the projection room of the cinema Every loudspeaker panel is equipped with eight two way speakers and eight amplifiers. multi-media installations, virtual-reality applica-tions, and even at live events such as open-air concerts. The Fraunhofer Institute in Ilmenau, Germany, offers the implementation and development of Wave Field Synthesis. Any applications in which sound quality and creative expression are important can make use of this new technology. Potential partners from every industry are welcome to experience the IOSONO system possibilities.For more information, please visit www.idmt.fraunhofer.de.

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