AES Barcelona 2005: Poster Session Z6


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	AES Barcelona 2005 Poster Session Z6 - Multichannel Sound

Last Updated: 20050401, mei

Monday, May 30, 09:30 — 11:00

Z6-1 An Approach to Discrete-Time Modeling Auralization for Wave Field Synthesis Applications—José Escolano, Basilio Pueo, Sergio Bleda, University of Alicante - Alicante, Spain; José Javier López, Technical University of Valencia - Valencia, Spain
In virtual room acoustics, the goal is to create the illusion of three-dimensional natural and realistic sound scenes. Accuracy of numerical methods in the discrete-time domain provides an explicit and practical way to synthesize impulsive responses of virtual rooms, especially in low frequency applications. On the other hand, advanced multichannel sound systems such as Wave Field Synthesis (WFS) allow the recreation of spatially wider sound scenes of sources after being convolved with extrapolated impulsive responses. In this paper the use of synthesized impulsive responses obtained by means of the finite-differences time domain method in auralization purposes using the WFS reproduction system is proposed and discussed. This method provides a complete solution of sound field variables, which are necessary to obtain a proper set of impulsive responses. Some examples are shown and evaluated to illustrate its applicability for WFS requirements.
Convention Paper 6425 (Purchase now)

Z6-2 Impression Differences by Placement of Front and Rear Microphones for Multichannel Stereo Recording—Toru Kamekawa, Tokyo National University of Fine Arts and Music - Toride, Ibaraki Pref., Japan
The impression differences of microphones arrays for multichannel stereophonic are considered. Optimum microphone array for the front three channels is presented by comparing localization and spatial impressions at several listening positions. From these experiments the array using omnidirectional microphones for left and right channels and a bidirectional microphone for center channel is evaluated better localization and spatial impression than the array using unidirectional (cardioid) microphones for left, right, and center channels specially at the off-center position. For the rear channels, the impression differences are compared by time differences between the front three microphones (Left, Right, Center) and two surround microphones using a pair comparison method. The result shows that spatial impression differs significantly between a certain number of time differences of frontal and rear microphones. Optimum position for surround microphones seems to be related to time differences between direct sound of the front microphones and early reflections of the rear microphones.
Convention Paper 6426 (Purchase now)

Z6-3 A New Microphone Technique for Five-Channel Recording—Geoff Martin, Bang & Olufsen a/s - Struer, Denmark
Contrary to widely-held belief, there are instances where multichannel sound reproduction results in a smaller sweet spot than in traditional two-channel stereo. This problem occurs due to interference in the listening room when signals in two or more channels are coherent. In contradistinction, interchannel coherence is required to ensure localization of sources and early reflections between (rather than in) the loudspeakers. This paper describes a new multichannel microphone configuration that can provide high interchannel coherence for direct sounds and low coherence for reverberation. Thus it considers not only the usual sound stage characteristics such as imaging and spaciousness but also unwanted artifacts caused by interchannel interference in the listening environment.
Convention Paper 6427 (Purchase now)

Z6-4 An Approach for Wave Field Synthesis High Power Applications—Basilio Pueo, José Escolano, Sergio Bleda, University of Alicante - Alicante, Spain; José Javier López, Technical University of Valencia - Valencia, Spain
Wave Field Synthesis (WFS) is a technique that enables true spatial reproduction over a large audience area with independence on the listener position. During the last decade, some major advances have been achieved for extending its use in every day applications. WFS can be applied to high powered applications, such as sound reinforcement events, in which true spatial audio would be needed. At present, dynamic midrange loudspeakers, which form the arrays needed to recreate the secondary sound sources cannot deliver such power because of their size. In this paper large-driver arrays are proposed to achieve high pressure fields that fulfill the requirements of high power applications. Size and distance between loudspeakers are chosen not to elevate the typical aliasing frequencies and directivity of the standard arrays. To prove the benefits of these arrays, two prototypes were constructed and measured. An analysis in the wave domain has shown that the sound field is properly reconstructed up to the theoretical aliasing frequency.
Convention Paper 6428 (Purchase now)

Z6-5 An Informal Comparison between Surround Sound Microphone Techniques—Rafael Kassier, Hyun-Kook Lee, Tim Brookes, Francis Rumsey, University of Surrey - Surrey, UK
Currently there is a lack of recorded test materials in 5-channel surround format. Particularly lacking are recordings made simultaneously using different microphone arrays that would allow comparative switching between different recorded versions of the same acoustical event. An ambitious pilot experiment was conducted involving the recording of various different program items using eight different recording techniques simultaneously. This was undertaken to determine the practicality of making such recordings, to allow informal comparisons between microphone techniques, and to create a set of simultaneous multichannel recordings for subsequent perceptual evaluation. This paper details experimental design considerations and practical limitations, as well as reporting initial observations regarding the resulting recordings.
Convention Paper 6429 (Purchase now)

Z6-6 A Loudspeaker-Based 3-D Sound Projection Using Virtual Microphone Control (ViMiC)—Jonas Braasch, McGill University - Montreal, Quebec, Canada
In auditory virtual environments it is often required to position an anechoic point source in three-dimensional space. When sources in such applications are to be displayed using multichannel loudspeaker reproduction systems, the processing is typically based upon simple amplitude-panning laws. This paper describes an alternative approach based on an array of virtual microphones. In the newly designed environment, the microphones, with adjustable directivity patterns and axis orientations, can be spatially placed as desired. The system architecture was designed to comply with the expectations of audio engineers and to create sound imagery similar to those associated with standard sound recording practice.
Convention Paper 6430 (Purchase now)

Z6-7 Detection of Subwoofer Depending on Crossover Frequency and Spatial Angle between Subwoofer and Main Speaker—Antti Kelloniemi, Jukka Ahonen, Olli Paajanen, Ville Pulkki, Helsinki University of Technology - Espoo, Finland
Since the direction of sound is not perceived at very low frequencies, it is feasible to use only one subwoofer for low frequency reproduction in commercial multichannel audio setups. A listening test was conducted to find the crossover frequency where the listeners begin to detect the subwoofer presence. The test was arranged in a symmetrical listening room using four pairs of loudspeakers, arranged symmetrically in four angles to the front of the listener to equalize the timbres as well as possible in reverberant conditions. The detection judgment was done using a version of the two alternatives forced choice (TAFC) adaptive method, with which the 75 percent point of the psychometric function was found. With the used sound samples the crossover frequency could be set to about 120 Hz before the subwoofer became detectable. No correlation was found between the highest acceptable crossover frequency and listening angle when the angel exceeded 30 degrees.
Convention Paper 6431 (Purchase now)