Wave Field Synthesis and MPEG-4

Audio Signal Processing for Next-Generation Multimedia Communication Systems, 2004

Conventional multichannel audio reproduction systems for entertainment or communication are not capable of immersing a large number of listeners in a well defined sound field. A novel technique for this purpose is the so-called wave field synthesis. It is based on the principles of wave physics and suitable for an implementation with current multichannel audio hard-and software components. A multiple number of fixed or moving sound sources from a real or virtual acoustic scene is reproduced in a listening area of arbitrary size. The listeners are not restricted in number, position, or activity and are not required to wear headphones. A successful implementation of wave field synthesis systems requires to address also spatial aliasing and the compensation of non-ideal properties of loudspeakers and of listening rooms.

The available technologies for the presentation of audiovisual scenes to large audiences show different degrees of maturity. While high quality physics based rendering of 3D scenes is found in many visual applications, the presentation of the accompanying audio content is based on much simpler technologies. Multi-channel cinema sound systems are only capable of delivering sound effects, but they do not faithfully reproduce an acoustic scene. New methods for acoustic rendering are required to provide physically correct recreation of audiovisual environments. A new technology for the reproduction of sound fields is based on Huygen's principle. It utilizes a large number (tens or hundreds) of loudspeakers to recreate a 3D sound field based on the physical description of the original acoustic environment. This paper describes different aspects of this technology, presents applications pursued by the European project CARROUSO and our own contributions to the project including the development of algorithms for loudspeaker and listening room compensation and real-time software implementation of a rendering software on a PC.

6th Int. Conference on Digital Audio Effects (DAFX-03), 2003

Wave Field Synthesis is a method for 3D sound reproduction, based on the precise construction of the desired wave field by using an array of loudspeakers. The main purpose of this work is to present a set of software tools that brings to the audio community a feasible an easy way to start working with wave field synthesis systems. First in the paper, an introduction to different 3D sound techniques and an overview of WFS theory and foundations are given. Next, a series of software tools specially developed to simulate, analyze and implement WFS systems are presented. The first software module helps the user in the design of the array of loudspeakers to be employed in the reproduction by computing the equations for each speaker signal excitation. Another tool simulates the wave field generated by the arrays and analyses both performance and quality of the acoustic field. Finally a user friendly tool for realtime convolution capable of producing the excitation signals for the array of loudspeakers is presented. Also, different experiments that have been carried out with this software in order to evaluate the precision and behaviour of different WFS configurations are presented and interpreted.

2003

Wave Field Synthesis is a method for 3D sound reproduction, based on the precise construction of the desired wave field by using an array of loudspeakers. The main purpose of this work is to present a set of software tools that brings to the audio community a feasible an easy way to start working with wave field synthesis systems. First

We present a new software system for spatial audio repro- duction called SoundScape Renderer. It is currently used for rendering 2-dimensional virtual acoustic scenes using either Wave Field Synthesis, binaural rendering or Vector Based Amplitude Panning. A further extension to higher order Am- bisonics is planned. However, in this paper we will focus on the WFS functionality. We also describe the physical setup of the WFS system in- stalled at the Usability Laboratory of Deutsche Telekom Lab- oratories, the natural habitat of the SoundScape Renderer. Finally, we present a working draft for an XML file for- mat enabling the exchange of acoustic scenes between differ- ent software systems. This Audio Scene Description Format (ASDF) is entirely open and we encourage everyone to par- ticipate in its further definition.

The SoundScape Renderer is a versatile software framework for real-time spatial audio rendering. The modular system architecture allows the use of arbitrary rendering methods. Three rendering modules are currently implemented: Wave Field Synthesis, Vector Base Amplitude Panning and Binaural Rendering. After a description of the software architecture, the implementation of the available rendering methods is explained and the graphical user interface is shown as well as the network interface for the remote control of the virtual audio scene. Finally, the Audio Scene Description Format, a system-independent storage file format, is briefly presented.

The Journal of the Acoustical Society of America, 1998

A multi-processor system is described for the production of virtual sound fields using small arrays of up to four high-quality loudspeakers and up to four control microphones distributed around an artificial head and torso in a lightly damped listening room. The digital signal processing engine consists of four floating point processors interconnected for parallel computation, together with digital and analog converters. The performance of the system is analyzed in terms of the tradeoff between the maximum sampling rates that can be used and the complexity of the digital filter matrices in the different operating modes of the system such as system identification, single-input multiple-error adaptive filtering, and full multichannel filtering with fixed coefficients.

Proc. of the, 2004

Since the early days of stereo good spatial sound impression had been limited to a small region, the so-called sweet spot. About 15 years ago the concept of wave field synthesis (WFS) solving this problem has been invented at TU Delft, but due to its computational complexity it has not been used outside universities and research institutes. Today the progress of microelectronics makes a variety of applications of WFS possible, like themed environments, cinemas, and exhibition spaces. This paper will highlight the basics of WFS and discuss some of the solutions beyond the basics to make it work in applications.