AES London 2011
Paper Session P4

P4 - Multichannel/Spatial, Part 1

Friday, May 13, 14:00 — 17:00 (Room 1)

Francis Rumsey

P4-1 3-D-Sound in Car Compartments Based on Loudspeaker Reproduction Using Crosstalk CancellationAndre Lundkvist, Arne Nykänen, Roger Johnsson, Luleå University of Technology - Luleå, Sweden
One way to enhance driving safety is to use signal sounds. Driver attention may further be improved by placing sounds in a 3-D space, using binaural synthesis. For correct loudspeaker reproduction of binaural signals, crosstalk between the channels needs to be canceled out. In this study, a crosstalk cancellation algorithm was developed and tested. The algorithm was applied in a car compartment, and three loudspeaker positions were compared. A listening test was performed to determine the subjects' ability to correctly localize sounds. It was shown that loudspeakers placed behind the listener correctly reproduced sound sources in the back hemisphere. Loudspeakers located in front and above the listener gave a high number of front/back confusions for all angles.
Convention Paper 8335 (Purchase now)

P4-2 Design of a Compact Cylindrical Loudspeaker Array for Spatial Sound ReproductionMihailo Kolundzija, Christof Faller, Ecole Polytechnique Fédérale de Lausanne - Lausanne, Switzerland; Martin Vetterli, Ecole Polytechnique Fédérale de Lausanne - Lausanne, Switzerland, University of California at Berkeley, Berkeley, CA, USA
Building acoustic beamformers is a problem whose solution is hindered by the wide-band nature of the audible sound. In order to achieve a consistent directional response over a wide range of frequencies, a conventional acoustic beamformer needs a high number of discrete loudspeakers and be large enough to achieve a desired low-frequency performance. The acoustic beamformer design described in this paper uses measurement-based optimal beamforming for loudspeakers located mounted on a rigid cylindrical baffle. Super-directional beamforming enables achieving desired directivity with multiple loudspeakers at low frequencies. High frequencies are reproduced with a single loudspeaker, whose highly directional reproduction—due to the cylindrical baffle—matches the design goals. In addition to the beamformer filter design procedure, it is shown how such loudspeaker array can be used for spatial sound reproduction.
Convention Paper 8336 (Purchase now)

P4-3 A New Multichannel Microphone Technique for Effective Perspective ControlHyunkook Lee, University of Huddersfield - Huddersfield, UK
This paper introduces a new multichannel microphone technique that was designed to produce multiple listener perspectives. A listener perspective paradigm and the related spatial attributes are also proposed for the evaluation of spatial quality in acoustic recording and reproduction. The proposed microphone array employs five coincident microphone pairs, which can be transformed into virtual microphones with different polar patterns and directions depending on the mixing ratio. The results of interchannel correlation and informal subjective evaluations suggest that the proposed technique is able to offer an effective control over various spatial attributes.
Convention Paper 8337 (Purchase now)

P4-4 Experimental Analysis of Spatial Properties of the Sound Field Inside a Car Employing a Spherical Microphone ArrayMarco Binelli, Andrea Venturi, Alberto Amendola, Angelo Farina, University of Parma - Parma, Italy
A 32-capsule spherical microphone array was employed for analyzing the spatial properties of the sound field inside a car. Both the background noise and the sound generated by the car's sound system were spatially analyzed, by superposing false-color sound pressure level maps over a panoramic 360x180 degree image, obtained with a parabolic-mirror camera. The analysis of the noise field revealed the parts of the car body where more noise is leaking in, providing guidance for better soundproofing. The analysis of the impulse responses generated by the loudspeakers did show useful information on the reflection patterns, providing guidance for adding absorbent material in selected locations and for optimizing position and orientation of loudspeakers.
Convention Paper 8338 (Purchase now)

P4-5 Improved ITU and Matrix Surround DownmixingChristof Faller, Illusonic LLC - St-Sulpice, Swtizerland; Pieter Schillebeeckx, Soundfield Ltd. - Wakefield, UK
Improvements to ITU and matrix surround downmixing are proposed. The surround channels are often mixed into the downmix with reduced gain to prevent that the resulting stereo signal is overly ambient. A method is proposed that allows control of the amount of ambience in the downmix signal independently of direct sound. In a conventional matrix surround downmix, ambience from the surround channels appears impaired (negatively correlated) . To address this issue, a technique is proposed that separates direct and ambient sound. Then, a matrix surround downmix is only applied to the direct sound, while ambient sound is treated like in an ITU downmix.
Convention Paper 8339 (Purchase now)

P4-6 Spaciousness Rating of 8-Channel Stereophony-Based Microphone ArraysLaurent Simon, University of Surrey - Guildford, Surrey, UK (now with INRIA – Rennes, Bretagne Atlantique, France); Russell Mason, University of Surrey - Guildford, Surrey, UK
In previous studies, the localization accuracy and the spatial impression of 3-2 stereo microphone arrays were discussed. These showed that 3-2 stereo cannot produce stable images to the side and to the rear of the listener. An octagon loudspeaker array was therefore proposed. Microphone array design for this loudspeaker configuration was studied in terms of localization accuracy, locatedness, and image width. This paper describes an experiment conducted to evaluate the spaciousness of 10 different microphone arrays used in different acoustical environments. Spaciousness was analyzed as a function of sound signal, acoustical environment, and microphone array's characteristics. It showed that the height of the microphone array and the original acoustical environment are the two variables that have the most influence on the perceived spaciousness, but that microphone directivity and the position of sound sources is also important.
Convention Paper 8340 (Purchase now)

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