AES San Francisco 2012
Paper Session P6

P6 - Spatial Audio Over Loudspeakers

Friday, October 26, 2:00 pm — 6:00 pm (Room 122)

Rhonda Wilson, Dolby Laboratories - San Francisco, CA, USA

P6-1 Higher Order Loudspeakers for Improved Surround Sound Reproduction in RoomsMark A. Poletti, Industrial Research Limited - Lower Hutt, New Zealand; Terence Betlehem, Industrial Research Limited - Lower Hutt, New Zealand; Thushara Abhayapala, Australian National University - Canberra, ACT, Australia
Holographic surround sound systems aim to accurately reproduce a recorded field in a small region of space around one or more listeners. This is possible at low frequencies with well-matched loudspeakers and acoustically treated rooms. At high frequencies the region of accurate reproduction shrinks and source localization is compromised. Furthermore, in typical rooms rooms reflections compromise quality. High quality reproduction therefore requires large numbers of loudspeakers and the use of techniques to reduce unwanted reverberation. This paper considers the use of higher-order loudspeakers that have multiple modes of radiation to offer an extended frequency range and zone of accurate reproduction. In addition, if a higher-order microphone is used for calibration, room effects can be effectively removed.
Convention Paper 8712 (Purchase now)

P6-2 A Model for Rendering Stereo Signals in the ITD-Range of HearingSiegfried Linkwitz, Linkwitz Lab - Corte Madera, CA, USA
Live sounds at a concert have spatial relationships to each other and to their environment. The specific microphone technique used for recording the sounds, the placement and directional properties of the playback loudspeakers, and the room’s response determine the signals at the listener’s ears and thus the rendering of the concert recording. For the frequency range, in which Inter-aural Time Differences dominate directional hearing, a free-field transmission line model will be used to predict the placement of phantom sources between two loudspeakers. Level panning and time panning of monaural sources are investigated. Effectiveness and limitations of different microphone pairs are shown. Recording techniques can be improved by recognizing fundamental requirements for spatial rendering. Observations from a novel 4-loudspeaker setup are presented. It provides enhanced spatial rendering of 2-channel sound.
Convention Paper 8713 (Purchase now)

P6-3 A Method for Reproducing Frontal Sound Field of 22.2 Multichannel Sound Utilizing a Loudspeaker Array FrameHiroyuki Okubo, NHK Science & Technology Research Laboratories - Setagaya-ku, Tokyo, Japan; Takehiro Sugimoto, NHK Science & Technology Research Laboratories - Setagaya-ku, Tokyo, Japan; Tokyo Institute of Technology - Midori-ku, Yokohama, Japan; Satoshi Oishi, NHK Science & Technology Research Laboratories - Setagaya-ku, Tokyo, Japan; Akio Ando, NHK Science & Technology Research Laboratories - Setagaya-ku, Tokyo, Japan
NHK has been developing Super Hi-Vision (SHV), an ultrahigh-definition TV system that has a 7,680 x 4,320 pixel video image and a 22.2 multichannel three-dimensional sound system. A loudspeaker array frame (LAF) integrated into a flat panel display can synthesize wavefront of frontal sound source and localize sound images on the display and back of the viewer by using technology to simulate sound propagation characteristics. This makes it possible to listen to 22.2 multichannel sound without installing 24 discrete loudspeakers surrounding the listener in the room. In this paper we describe the prototype of the LAF and its performance focusing on frontal sound reproduction.
Convention Paper 8714 (Purchase now)

P6-4 Low-Frequency Temporal Accuracy of Small-Room Sound ReproductionAdam J. Hill, University of Derby - Derby, Derbyshire, UK; Malcolm O. J. Hawksford, University of Essex - Colchester, Essex, CO4 3SQ, UK
Small-room sound reproduction is strongly affected by room-modes in the low-frequency band. While the spectral impact of room-modes is well understood, there is less information on how modes degrade the spatiotemporal response of a sound reproduction system. This topic is investigated using a bespoke finite-difference time-domain (FDTD) simulation toolbox to virtually test common subwoofer configurations using tone bursts to judge waveform fidelity over a wide listening area. Temporal accuracy is compared to the steady-state frequency response to determine any link between the two domains. The simulated results are compared to practical measurements for validation.
Convention Paper 8715 (Purchase now)

P6-5 Experiments of Sound Field Reproduction Inside Aircraft Cabin Mock-UpPhilippe-Aubert Gauthier, Université de Sherbrooke - Sherbrooke, Quebec, Canada; McGill University - Montreal, Quebec, Canada; Cédric Camier, Université de Sherbrooke - Sherbrooke, Quebec, Canada; McGill University - Montreal, Quebec, Canada; Felix A. Lebel, Université de Sherbrooke - Sherbrooke, Quebec, Canada; Y. Pasco, Université de Sherbrooke - Sherbrooke, Quebec, Canada; McGill University - Montreal, Quebec, Canada; Alain Berry, Université de Sherbrooke - Sherbrooke, Quebec, Canada; McGill University - Montreal, Quebec, Canada
Sound environment reproduction of various flight conditions in aircraft mock-ups is a valuable tool for the study, prediction, demonstration, and jury testing of interior aircraft sound quality and comfort. To provide a faithful reproduced sound environment, time, frequency, and spatial characteristics should be preserved. Physical sound field reproduction approaches for spatial sound reproduction are mandatory to immerse the listener body in the proper sound field so that localization cues are recreated. Vehicle mock-ups pose specific problems for sound field reproduction. Confined spaces, needs for invisible sound sources, and a singular acoustical environment make the use of open-loop sound field reproduction technologies not ideal. In this paper preliminary experiments in an aircraft mock-up with classical multichannel least-square methods are reported. The paper presents objective evaluations of reproduced sound fields. Promising results along with practical compromises are reported.
Convention Paper 8716 (Purchase now)

P6-6 Wave Field Synthesis with Primary Source Correction: Theory, Simulation Results, and Comparison to Earlier ApproachesFlorian Völk, Technische Universitaet Muenchen - München, Germany; Hugo Fastl, Technical University of Munich - Munich, Germany
Wave field synthesis (WFS) with primary source correction (PSC) extends earlier theoretical derivations by the correct synthesis of primary point sources at a reference point. In this paper the theory of WFS with PSC is revised with respect to other derivations, extended for the application to focus points and validated by numerical simulation. A comparison to earlier approaches to WFS concludes the paper.
Convention Paper 8717 (Purchase now)

P6-7 Limitations of Point-Source Sub-Woofer Array Models for Live SoundAmbrose Thompson, Martin Audio - High Wycombe, UK; Josebaitor Luzarraga Iturrioz, Martin Audio - High Wycombe, UK; Phil Anthony, Martin Audio - High Wycombe, UK
This paper examines the validity of applying simple models to the kind of highly configurable, low frequency arrays typically used for live sound. Measurements were performed on a single full-sized touring sub-woofer array element at different positions within a number of different array configurations. It was discovered that radiation was rarely omnidirectional and in some cases more than 20 dB from being so. Additionally, the in-situ polar response significantly differed from that obtained with the cabinet in isolation, the degree of difference (2–10 dB) was strongly dependent on array type and element position. For compact arrays we demonstrate, via the application of the “acoustic center” concept, that even when elemental radiation approaches omnidirectional behavior some array configurations are particularly susceptible to errors arising from commonly applied assumptions.
Convention Paper 8718 (Purchase now)

P6-8 Improved Methods for Generating Focused Sources Using Circular ArraysMark A. Poletti, Industrial Research Limited - Lower Hutt, New Zealand
Circular loudspeaker arrays allow the reproduction of 2-D sound fields due to sources outside the loudspeaker radius. Sources inside the array can be approximated by focusing sound from a subset of the loudspeakers to a point. The resulting sound field produces the required divergence of wave fronts in a half-space beyond the focus point. This paper presents two new methods for generating focused sources that produce lower errors than previous approaches. The first derives an optimum window for limiting the range of active loudspeakers by matching the field to that of a monopole inside the source radius. The second applies pressure matching to a monopole source over a region where the wavefronts are diverging.
Convention Paper 8719 (Purchase now)

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