AES London 2010
Poster Session P26

Tuesday, May 25, 14:00 — 15:30 (Room C4-Foyer)

P26 - Recording, Production, and Reproduction—Multichannel and Spatial Audio

P26-1 Evaluation of Virtual Source Localization Using 3-D Loudspeaker SetupsFlorian Keiler, Johann-Markus Batke, Technicolor, Research, and Innovation - Hannover Germany
This paper evaluates the localization accuracy of different playback methods for 3-D spatial sound using a listening test. The playback methods are characterized by their panning functions that define the gain for each loudspeaker to play back a sound source positioned at a distinct pair of azimuth and elevation angles. The tested methods are Ambisonics decoding using the mode matching approach, vector base amplitude panning (VBAP), and a newly proposed 3-D robust panning approach. For irregular 3-D loudspeaker setups, as found in home environments, the mode matching shows poor localization. The new 3-D robust panning leads to a better localization and can also outperform the VBAP technology dependent on the source position and the loudspeaker setup used.
Convention Paper 8060 (Purchase now)

P26-2 Optimization of the Localization Performance of Irregular Ambisonic Decoders for Multiple Off-Center ListenersDavid Moore, Glasgow Caledonian University - Glasgow, Lanarkshire, UK; Jonathan Wakefield, University of Huddersfield - Huddersfield, West Yorkshire, UK
This paper presents a method for optimizing the performance of irregular Ambisonic decoders for multiple off-center listeners. New off-center evaluation criteria are added to a multi-objective fitness function, based on auditory localization theory, which guides a heuristic search algorithm to derive decoder parameter sets for the ITU 5-speaker layout. The new evaluation criteria are based upon Gerzon’s Metatheory of Auditory Localization and have been modified to take into account off-center listening positions. The derived decoders exhibit improved theoretical localization performance for off-center listeners. The theoretical results are supported by initial listening test results.
Convention Paper 8061 (Purchase now)

P26-3 Vibrational Behavior of High Aspect Ratio Multiactuator PanelsBasilio Pueo, Jorge A. López, Javier Moralejo, University of Alicante - Alicante, Spain; José Javier López, Technical University of Valencia - Valencia, Spain
Multiactuator Panels (MAPs) consist of a flat panel of a light and stiff material to which a number of mechanical exciters are attached, creating bending waves that are then radiated as sound fields. MAPs can substitute the traditional dynamic loudspeaker arrays for Wave Field Synthesis (WFS) with added benefits, such as the low visual profile or omnidirectional radiation. However, the exciter interaction with the panel, the panel material, and the panel edge boundary conditions are some of the critical points that need to be evaluated and improved. In this paper the structural acoustic behavior of a high aspect ratio MAP is analyzed for two classical edge boundary conditions: free and clamped. For that purpose, the surface velocity over the whole area of the MAP prototype has been measured with a Laser Doppler Vibrometer (LDV), which helped in understanding the sound-generating behavior of the panel.
Convention Paper 8062 (Purchase now)

P26-4 Design of a Circular Microphone Array for Panoramic Audio Recording and Reproduction: Microphone DirectivityHüseyin Hacihabiboglu, Enzo De Sena, Zoran Cvetkovic, King's College London - London, UK
Design of a circularly symmetric multichannel recording and reproduction system is discussed in this paper. The system consists of an array of directional microphones evenly distributed on a circle and a matching array of loudspeakers. The relation between the microphone directivity and the radius of the circular array is established within the context of time-intensity stereophony. The microphone directivity design is identified as a constrained linear least squares optimization problem. Results of a subjective evaluation are presented that indicate the usefulness of the proposed microphone array design technique.
Convention Paper 8063 (Purchase now)

P26-5 Design of a Circular Microphone Array for Panoramic Audio Recording and Reproduction: Array RadiusEnzo De Sena, Hüseyin Hacihabiboglu, Zoran Cvetkovic, King's College London - London, UK
A multichannel audio system proposed by Johnston and Lam aims at perceptual reconstruction of the sound field of an acoustic performance in its original venue. The system employs a circular microphone array, of 31 cm diameter, to capture relevant spatial cues. This design proved to be effective in the rendition of the auditory perspective, however other studies showed that there is still substantial room for improvement. This paper investigates the impact of the array diameter on the width and naturalness of the auditory images. To this end we propose a method for quantification and prediction of the perceived naturalness. Simulation results support array diameters close to that proposed by Johnston and Lam in the sense that they achieve optimal naturalness in the center of the listening area, but also suggest that larger arrays might provide a more graceful degradation of the naturalness for listening positions away from the center.
Convention Paper 8064 (Purchase now)

P26-6 MIAUDIO—Audio Mixture Digital MatrixDavid Pedrosa Branco, José Neto Vieira, Iouliia Skliarova, Universidade de Aveiro - Aveiro, Portugal
Electroacoustic music is turning more and more to the sound diffusion techniques. Multichannel sound systems like BEAST and SARC are built so that the musician can independently control the intensity of several audio channels. This feature provides the possibility of creating several sound diffusion scenarios, i.e., immersion and the possibility of movement around the audience. The developed system (MIAUDIO) is a real-time sound diffusion system currently able to mix up to 8 audio input channels through 32 output channels. A hardware solution was adopted using a Field Programmable Gate Array (FPGA) to perform the mixture. The analog audio signals are conditioned, converted to digital format by several analog-to-digital converters, and then sent to the FPGA that is responsible to perform the mixing algorithm. The host computer connects to the FPGA via USB and is responsible for supplying the parameters that define the audio mixture. Being so, the user has control over the input levels through the output channels independently. MIAUDIO was successfully implemented with a low-cost solution when compared with similar systems. All the channels were tested using a Precision One system with very good results.
Convention Paper 8065 (Purchase now)

P26-7 The Perception of Focused Sources in Wave Field Synthesis as a Function of Listener AngleRobert Oldfield, Ian Drumm, Jos Hirst, University of Salford - Salford, UK
Wave field synthesis (WFS) is a volumetric sound reproduction technique that allows virtual sources to be positioned anywhere in space. The reproduction of the wave field of these sources means they can be accurately localized even when placed in front of the secondary sources/loudspeakers. Such “focused sources” are very important in WFS as they greatly add to the realism of an auditory scene, however the perception and localization-ability changes with listener and virtual source position. In this paper we present subjective tests to determine the localization accuracy as a function of angle, defining the subjective “view angle.” We also show how improvements can be made through the addition of the first order image sources.
Convention Paper 8066 (Purchase now)

P26-8 Gram-Schmidt-Based Downmixer and Decorrelator in the MPEG Surround CodingDer-Pei Chen, Hsu-Feng Hsiao, Han-Wen Hsu, Chi-Min Liu, National Chiao Tung University - Hsinchu, Taiwan
MPEG Surround (MPS) coding is an efficient method for multichannel audio coding. In MPS coding, downmixing from multichannel signals into a fewer number of channels is an efficient way to achieve a high compression rate in an encoder. In decoder, an upmixing module combining with the decorrelator is the key module to reconstruct the multichannel signals. This paper considers the design of the downmixer and the decorrelator through the Gram-Schmidt orthogonal process. The individual and joint effects from the downmixer and decorrelator are verified through intensive subjective and objective quality measure.
Convention Paper 8067 (Purchase now)