AES San Francisco 2008
Paper Session P9
Multichannel Sound Reproduction
Friday, October 3, 2:30 pm — 6:30 pm
: Durand Begault
, NASA Ames Research Center - Mountain View, CA, USAP9-1 An Investigation of 2-D Multizone Surround Sound Systems
, Industrial Research Limited - Lower Hutt, Wellington, New Zealand
Surround sound systems can produce a desired sound field over an extended region of space by using higher order Ambisonics. One application of this capability is the production of multiple independent soundfields in separate zones. This paper investigates multi-zone surround systems for the case of two-dimensional reproduction. A least squares approach is used for deriving the loudspeaker weights for producing a desired single frequency wave field in one of N
zones. It is shown that reproduction in the active zone is more difficult when an inactive zone is in-line with the virtual sound source and the active zone. Methods for controlling this problem are discussed.
Convention Paper 7551 (Purchase now)P9-2 Two-Channel Matrix Surround Encoding for Flexible Interactive 3-D Audio Reproduction
, Creative Advanced Technology Center - Scotts Valley, CA, USA
The two-channel matrix surround format is widely used for connecting the audio output of a video gaming system to a home theater receiver for multichannel surround reproduction. This paper describes the principles of a computationally-efficient interactive audio spatialization engine for this application. Positional cues including 3-D elevation are encoded for each individual sound source by frequency-independent interchannel phase and amplitude differences, rather than HRTF cues. A matrix surround decoder based on frequency-domain Spatial Audio Scene Coding (SASC) is able to faithfully reproduce both ambient reverberation and positional cues over headphones or arbitrary multichannel loudspeaker reproduction formats, while preserving source separation despite the intermediate encoding over only two channels.
Convention Paper 7552 (Purchase now)P9-3 Is My Decoder Ambisonic?
, SRI International - Menlo Park, CA, USA; Richard Lee
, Pandit Littoral - Cooktown, Queensland, Australia; Eric Benjamin
, Dolby Laboratories - San Francisco, CA, USA
In earlier papers, the present authors established the importance of various aspects of Ambisonic decoder design: a decoding matrix matched to the geometry of the loudspeaker array in use, phase-matched shelf filters, and distance compensation. These are needed for accurate reproduction of spatial localization cues, such as interaural time difference (ITD), interaural level difference (ILD), and distance cues. Unfortunately, many listening tests of Ambisonic reproduction reported in the literature either omit the details of the decoding used or utilize suboptimal decoding. In this paper we review the acoustic and psychoacoustic criteria for Ambisonic reproduction; present a methodology and tools for "black box" testing to verify the performance of a candidate decoder; and present and discuss the results of this testing on some widely used decoders.
Convention Paper 7553 (Purchase now)P9-4 Exploiting Human Spatial Resolution in Surround Sound Decoder Design
—David Moore, Jonathan Wakefield
, University of Huddersfield - West Yorkshire, UK
This paper presents a technique whereby the localization performance of surround sound decoders can be improved in directions in which human hearing is more sensitive to sound source location. Research into the Minimum Audible Angle is explored and incorporated into a fitness function based upon a psychoacoustic model. This fitness function is used to guide a heuristic search algorithm to design new Ambisonic decoders for a 5-speaker surround sound layout. The derived decoder is successful in matching the variation in localization performance of the human listener with better performance to the front and rear and reduced performance to the sides. The effectiveness of the standard ITU 5-speaker layout versus a non-standard layout is also considered in this context.
Convention Paper 7554 (Purchase now)P9-5 Surround System Based on Three-Dimensional Sound Field Reconstruction
—Filippo M. Fazi, Philip A. Nelson, Jens E. Christensen
, University of Southampton - Southampton, UK; Jeongil Seo
, Electronics and Telecommunications Research Institute (ETRI) - Daejeon, Korea
The theoretical fundamentals and the simulated and experimental performance of an innovative surround sound system are presented. The proposed technology is based on the physical reconstruction of a three-dimensional target sound field over a region of the space using an array of loudspeakers surrounding the listening area. The computation of the loudspeaker gains includes the numerical or analytical solution of an integral equation of the first kind. The experimental setup and the measured reconstruction performance of a system prototype constituted by a three dimensional array of 40 loudspeakers are described and discussed.
Convention Paper 7555 (Purchase now)P9-6 A Comparison of Wave Field Synthesis and Higher-Order Ambisonics with Respect to Physical Properties and Spatial Sampling
—Sascha Spors, Jens Ahrens
, Technische Universität Berlin - Berlin, Germany
Wave field synthesis (WFS) and higher-order Ambisonics (HOA) are two high-resolution spatial sound reproduction techniques aiming at overcoming some of the limitations of stereophonic reproduction techniques. In the past, the theoretical foundations of WFS and HOA have been formulated in a quite different fashion. Although some work has been published that aims at comparing both approaches their similarities and differences are not well documented. This paper formulates the theory of both approaches in a common framework, highlights the different assumptions made to derive the driving functions, and the resulting physical properties of the reproduced wave field. Special attention will be drawn to the spatial sampling of the secondary sources since both approaches differ significantly here.
Convention Paper 7556 (Purchase now)P9-7 Reproduction of Virtual Sound Sources Moving at Supersonic Speeds in Wave Field Synthesis
—Jens Ahrens, Sascha Spors
, Technische Universität Berlin - Berlin, Germany
In conventional implementations of wave field synthesis, moving sources are reproduced as sequences of stationary positions. As reported in the literature, this process introduces various artifacts. It has been shown recently that these artifacts can be reduced when the physical properties of the wave field of moving virtual sources are explicitly considered. However, the findings were only applied to virtual sources moving at subsonic speeds. In this paper we extend the published approach to the reproduction of virtual sound sources moving at supersonics speeds. The properties of the actual reproduced sound field are investigated via numerical simulations.
Convention Paper 7557 (Purchase now)P9-8 An Efficient Method to Generate Particle Sounds in Wave Field Synthesis
—Michael Beckinger, Sandra Brix
, Fraunhofer Institute for Digital Media Technology - Ilmenau, Germany
Rendering a couple of virtual sound sources for wave field synthesis (WFS) in real time is nowadays feasible using the calculation power of state-of-the-art personal computers. If immersive atmospheres containing thousands of sound particles like rain and applause should be rendered in real time for a large listening area with a high spatial accuracy, calculation complexity increases enormously. A new algorithm based on continuously generated impulse responses and following convolutions, which renders many sound particles in an efficient way will be presented in this paper. The algorithm was verified by first listening tests and its calculation complexity was evaluated as well.
Convention Paper 7558 (Purchase now)