System Applicability

The auralization techniques find vast applications in the areas of virtual reality, 3D musical production, multimedia telecommunications and immersive television, allowing to increase the degree of realism of the visual presentation, and to add context-aware spatial information.

Consider, as an example, an application in aeronautical engineering design, where designers navigate around an airplane mockup, for instance interested in inspecting the air flow throughout the fuselage. The noise associated with the air turbulent behavior and with the different sound intensities in the diverse points of the fuselage could be added to the visual navigation, offering a set of acoustics information relevant to the design, bringing the simulated reality to the reach of the designer.

In a design for insulation and treatment of the internal noise for an airplane the audiovisual navigation inside of the virtual mockup would allow, for example, to evaluation of the sound quality and sound intensity in distinct points of the cabin, assisting in the identification of isolated problems, imperfections, and in one better tunning of the project. A physically-correct auralization of the sound field would be necessary for such activities in conception and engineering projects.

Applications directed toward improvement or conception of new multimedia services each time more request greater realism and quality in the presentation of the visual and sound material. It has an enormous appeal in the musical production and interactive digital audio consumption in personal players. For some applications, for example the development of new generations of teleconference, videofone or interactive television, it has an enormous interest in three-dimensional models, that can reconstruct the remote audiovisual reality, which is three-dimensional.

Systems oriented to telepresence or sophisticated proposals for immersive teleconference already consider the use of holographic or stereo images, not only to transmit with realism the remote space characteristics, but also aiming at producing a more fluid visual interface binding the remote sites. Stereoscopy and 3D auralization would allow together a fusion of the remote sites on a gradual uniform way, or could carry the users to a new environment, where the visual properties and 3D acoustics can be shared.

New generations of telepresence systems where the capture of multiple projections is a reality also could adopt the capture of 3D audio, taking into account its directional properties. With the use of fast networks (for example, Gigabit Ethernet) and of adequate techniques for multichannel multimedia compression and multiprojection, it becomes possible to investigate the limits and to exercise the creative capacity in the conception of sophisticated applications of 3D multimedia transmission and rendering.

A soundfield microphone coupled to an 3D audio coding technique, as for example Ambisonics, could be used to carry through the capture and the transmission of the 3D sound field from a place to another. The sound canals can adequately be codified and integrated to video streams, opening enormous possibilities of interaction, conception of new applications and services, contemplating the 3D audio and video fusion.

In the area of digital television (DTV) new applications associating the transmission and reproduction of 3D acoustic environments are already viable with systems based on 5.1 channels, and even 7.1. Enhanced surround systems employing more channels are now under tests, for instance in the Japanese ISDB system, and are being considered also in the newer Brazilian DTV system. Thanks to state-of-the-art audio codecs (e.g. MPEG-4 AAC) one can deliver today even dozens of audio channels, capable of conveying complex spatial audio information. However they still consist of higher cost applications and little explored in respect of content production possibilities, interaction and realism enhancement.

We consider a future goal in applications for the Digital Cave the conception and the prototyping of an application with integrated capture, transmission and 3D audio and video rendering, that can be portable for complete immersive virtual reality applications, as well as advanced applications for digital TV.

We identify several application areas, both in architecture design and actual system developments:

• function modularization or separation within the audio processing chain, which can be implemented in different devices or software components
• permit the functional reconfigurability or scalability by adding or excluding functions (reconfigurable complexity)
• integrated system for auralization of an audiovisual scene described with X3D, VRML, MPEG-4 or other scene description format
• creation of sound environments and complex musical scenes, by adding sound sources in the virtual space (orchestration applications)
• acoustical scene edition, positioning objects and sound sources in space
• surround sound field projection for usage in shows, theaters, auditorium, multimedia presentation, etc.
• permit the portability and interoperation of software and devices, carrying out audio functions, by standardizing the signals of importance flowing between adjacent functional layers, which every component (software or hardware) should produce at the interfaces with other components.