AES Warsaw 2015
Paper Session P15

P15 - (Lecture) Spatial Audio—Part 2

Sunday, May 10, 09:00 — 12:30 (Room: Belweder)

Ville Pulkki, Aalto University - Espoo, Finland

P15-1 Analysis on the Timbre Coloration of Wave Field Synthesis Using a Binaural Loudness ModelBosun Xie, South China University of Technology - Guangzhou, China; Haiming Mai, South China University of Technology - Guangzhou, China; Yang Liu, South China University of Technology - Guangzhou, China; Xiaoli Zhong, South China University of Technology - Guangzhou, China
Wave field synthesis (WFS) aims to reconstruct a target sound field within an extending region. An ideal WFS system requires continuous loudspeakers array. Discrete loudspeaker array in practical WFS causes spatial aliasing errors above the Nyquist frequency limit, and thus results in timbre coloration. The present work analyzes the timbre in WFS using Moore’s modified binaural loudness model, in which the binaural loudness level spectra is used as a criterion to evaluate the timbre coloration. The results prove that timbre coloration reduces with the increasing distance between field point and active loudspeakers; and reducing the space between adjacent loudspeakers reduces perceivable timbre coloration. A psychoacoustic experiment yields consistent results with those of analysis, and therefore validates the proposed method.
Convention Paper 9320 (Purchase now)

P15-2 Physical Properties of Local Wave Field Synthesis Using Linear Loudspeaker ArraysFiete Winter, University of Rostock - Rostock, Germany; Sascha Spors, University of Rostock - Rostock, Germany
Wave Field Synthesis aims at a physically accurate synthesis of a desired sound field inside an extended listening area. Due to limitation of practical loudspeaker setups, the accuracy of this sound field synthesis technique over the entire listening area is limited. Local Wave Field Synthesis narrows the spatial extent down to a local listening area in order to improve the reproduction accuracy inside this limited region. Recently a method has been published, which utilizes focused sources as a distribution of more densely placed virtual secondary sources around the local area. Within this paper an analytical framework is established to analyze the physical properties of this approach for linear loudspeaker setups.
Convention Paper 9321 (Purchase now)

P15-3 Pressure-Matching Beamforming Method for Loudspeaker Arrays with Frequency Dependent Selection of Control PointsFerdinando Olivieri, University of Southampton - Southampton, Hampshire, UK; Filippo Maria Fazi, University of Southampton - Southampton, Hampshire, UK; Mincheol Shin, ISVR, University of Southampton - Southampton, Hampshire, UK; Philip Nelson, ISVR, University of Southampton - Southampton, UK
The Pressure-Matching Method (PMM) is a signal processing technique used to generate the digital filters required by a loudspeaker array to reproduce a desired sound field. System performance depends on the choice of a number of parameters of the numerical algorithm, such as the target field and the regularization factor. If a target sound field is chosen with large amplitude variation between the so-called control points, performance might also depend on the relative distance between these points in relation to a the wavelength of the sound to be reproduced. If this distance is too small, the accuracy of the reproduced field may be reduced at the listener location. A strategy is proposed to improve the PMM that is based on a frequency-dependent selection of the control points that contribute to the PMM cost function. By means of numerical simulations and experiments in anechoic environment, it is shown that the proposed method allows for accurate control of the response of the reproduced field at the listener location.
Convention Paper 9322 (Purchase now)

P15-4 Discussion of the Wavefront Sculpture Technology Criteria for Straight Line ArraysFrank Schultz, University of Rostock / Institute of Communications Engineering - Rostock, Germany; Florian Straube, TU Berlin - Berlin, Germany; Sascha Spors, University of Rostock - Rostock, Germany
Wavefront Sculpture Technology introduced line source arrays for large scale sound reinforcement, aiming at the synthesis of highly spatial-aliasing free sound fields for full audio bandwidth. The paper revisits this technology and its criteria for straight arrays using a signal processing model from sound field synthesis. Since the latest array designs exhibit very small driver distances, the sampling condition for grating lobe free electronic beam forming regains special interest. Furthermore, a discussion that extends the initial derivations of the spatial lowpass characteristics of circular and line pistons and line pistons with wavefront curvature applied in subarrays is given.
Convention Paper 9323 (Purchase now)

P15-5 Sound Field Synthesis of Virtual Cylindrical Waves Using Circular and Spherical Loudspeaker ArraysNara Hahn, University of Rostock - Rostock, Germany; Sascha Spors, University of Rostock - Rostock, Germany
In sound field synthesis, like near-field compensated higher-order Ambisonics or Wave Field Synthesis, various virtual source models are used to describe a virtual sound scene. In near-field compensated higher-order Ambisonics, the virtual sound field has to be expanded into spherical harmonics. Unlike plane waves or spherical waves, cylindrical waves are not conveniently represented in the spherical harmonics domain. In this paper we tackle this problem and derive closed form driving functions for virtual cylindrical waves. The physical properties of synthesized sound fields are investigated through numerical simulations, where the results are compared with virtual cylindrical waves in wave field synthesis.
Convention Paper 9324 (Purchase now)

P15-6 Perceptual Band Allocation (PBA) for the Rendering of Vertical Image Spread with a Vertical 2D Loudspeaker ArrayHyunkook Lee, University of Huddersfield - Huddersfield, UK
A series of subjective experiments were conducted to investigate a novel vertical image rendering method named “Perceptual Band Allocation (PBA),” using octave bands of pink noise with a vertical 2D reproduction setup with main and height loudspeaker pairs. The perceived height of each octave band was first measured for the main and height loudspeakers individually. Results suggested a significant difference between monophonic and stereophonic images in the perceived relationship between frequency and height. Six different test conditions have been created aiming for various degrees of vertical image spread, in such a way that each frequency band was mapped to either the main or height loudspeaker layer based on the results from the localization experiment. Multiple comparison tests were conducted to grade the perceived magnitude of vertical image spread. It was generally found that various degrees of vertical image spread could be rendered using different PBA schemes, but the perceived results did not fully match predicted results based on the localization results. Differences between the main and height loudspeaker layers in the spectral weightings of ear-input signal at certain frequencies was identified as one of the factors that influenced this result.
Convention Paper 9325 (Purchase now)

P15-7 Synthesis of Moving Reverberation Using Active Acoustics—Preliminary ReportJung Wook (Jonathan) Hong, McGill University - Montreal, QC, Canada; GKL Audio Inc. - Montreal, QC, Canada; Wieslaw Woszczyk, McGill University - Montreal, QC, Canada; Durand R. Begault, NASA Ames Research Center - Moffett Field, CA, USA; David Benson, McGill University - Montreal, Quebec, Canada; The Centre for Interdisciplinary Research in Music Media and Technology - Montreal, Quebec, Canada
An ambient sound field created artificially using active acoustics (virtual acoustics) attempts to resurrect the perceived naturalness of the original architectural space and the distinct responsiveness to musical sound sources. Moving reverberation is typically associated with coupled volumes contained within a larger architectural space where each volume is activated by a sound source at a different moment in time due to propagation delay. The produced energy has a diverse characteristic rate of decay with which its energy is mixed within the common space causing multiple slopes on the decay. This causes a sensation of a decaying diffused sound that is not homogenized but distinctly appearing in different zones of the space as a shifting acoustic energy. In order to reconstruct the moving reverberation, an active acoustics system was used to render an ambient sound field from measured impulse responses of large architectural space, the Grace Cathedral in San Francisco.
Convention Paper 9326 (Purchase now)

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