AES New York 2009
Poster Session P19

P19 - Arrays

Monday, October 12, 10:00 am — 11:30 am
P19-1 Control of Acoustic Radiation Pattern in a Dual-Dipole Array—Mincheol Shin, Philip Nelson, University of Southampton - Highfield, Southampton, UK
This paper proposes a control strategy for generating various acoustic radiation patterns associated with a “personalized sound field” using an acoustic source array. A dual-dipole array, which models each loudspeaker as an imperfect dipole and a source signal control algorithm, which effectively considers both energy difference maximization and radiation efficiency are introduced in order to obtain better radiation patterns for generating the desired sound field. With the proposed dual dipole array and control algorithm, a wide controllability from a comparatively low to a high frequency range is obtained, although the array size is small enough to implement in mobile applications. Conceptually novel control strategy proposed enables to cancel out the backward radiation efficiently. The performance of the dual dipole source array is verified by using computer simulations.
Convention Paper 7949 (Purchase now)

P19-2 A Novel Beam-Forming Loudspeaker System Using Digitally Driven Speaker System—Kyosuke Watanabe, Akira Yasuda, Hajime Ohtani, Ryota Suzuki, Naoto Shinkawa, Tomohiro Tsuchiya, Kenzo Tsuihiji, Hosei University - Koganei, Tokyo, Japan
In this paper we propose a beam-forming loudspeaker based on digitally direct driven loudspeaker system (digital-SP); the proposed speaker employs multi-bit delta-sigma modulation in addition to a line speaker array and a delay circuit. The proposed speaker can be realized only by D flip-flops and digital-SP. Delay elements are introduced between the mismatch shaper and sub-loudspeakers, and beam-forming is realized without degradation of the noise shaping performance of the multi-bit DSM. By using a small amount of additional hardware, we can easily control the sound direction. If a beam-forming loudspeaker can be driven digitally, all processes can be performed digitally without the use of analog components such as power amplifiers, and a small, light, high-quality speaker system can be realized. The prototype is constructed using an FPGA, CMOS drivers, and a line speaker array. The effectiveness has been confirmed by using measurement data. A gain of 8 dB or more is measured relative to the normal digital speaker system. An attenuation of 14.7dB for 40° direction is measured.
Convention Paper 7950 (Purchase now)

P19-3 Speaker Array System Based on Equalization Method with a Quiet Zone—Soonho Baek, Myung-Suk Song, Yonsei University - Seoul, Korea; Seok-Pil Lee, Korea Electronics Technology Institute - Seongnam, Korea; Hong-Goo Kang, Yonsei University - Seoul, Korea
This paper proposes an equalization-based loudspeaker array system to form a consistent sound spot to listeners under reverberant environment. To overcome the poor sound quality of conventional beamforming methods in a reverberant environment, the proposed method designs a novel criterion to reproduce as close as possible sound to the original source at the target point as well as to make null at specified points located in the quiet zone. Simulation results with a 16-channel loudspeaker array system confirm the superiority of the proposed method. In addition, we also verify that the sound pressure level of the quiet zone depends on the number and the area of quiet points.
Convention Paper 7951 (Purchase now)

P19-4 On the Secondary Source Type Mismatch in Wave Field Synthesis Employing Circular Distributions of Loudspeakers—Jens Ahrens, Sascha Spors, Deutsche Telekom Laboratories, Techniche Universität Berlin - Berlin, Germany
The theory of wave field synthesis has been formulated for linear and planar arrays of loudspeakers but has been found to be also applicable with arbitrary convex loudspeaker contours with acceptable error. The main source of error results from the fact that the required properties of the employed loudspeakers are dictated by the Neumann Green’s function of the array geometry under consideration. For nonlinear and nonplanar arrays a systematic error arises that is a result of the mismatch between the spatio-temporal transfer function of the loudspeakers and the Neumann Green’s function of the loudspeaker contour under consideration. We investigate this secondary source type mismatch for the case of circular distributions of loudspeakers.
Convention Paper 7952 (Purchase now)

P19-5 A Configurable Microphone Array with Acoustically Transparent Omnidirectional Elements—Jonathan S. Abel, Nicholas J. Bryan, Travis Skare, Miriam Kolar, Patty Huang, Stanford University - Stanford, CA, USA; Darius Mostowfi, Countryman Associates, Inc. - Menlo Park, CA, USA; Julius O. Smith III, Stanford University - Stanford, CA, USA
An acoustically transparent, configurable microphone array with omnidirectional elements, designed for room acoustics analysis and synthesis and archaeological acoustics applications, is presented. Omnidirectional microphone elements with 2 mm-diameter capsules and 1 mm-diameter wire mounts produce a nearly acoustically transparent array, and provide a simplified mathematical framework for processing measured signals. The wire mounts are fitted onto a 1.6 cm-diameter tube forming the microphone stand, with the microphones arranged above the tube so that acoustic energy can propagate freely across the array. The wire microphone mounts have some flexibility, and the array may be configured. Detachable arms with small speakers are used to estimate the element positions with an accuracy better than the 2 mm microphone diameter.
Convention Paper 7953 (Purchase now)

P19-6 Microphone Array Synthetic Reconfiguration—Yoomi Hur, Stanford University - Stanford, CA, USA, Yonsei University, Seoul, Korea; Jonathan S. Abel, Stanford University - Stanford, CA, USA; Young-cheol Park, Yonsei University - Wonju, Korea; Dae Hee Youn, Yonsei University - Seoul, Korea
This paper describes methods for processing signals recorded at a microphone array so as to estimate the signals that would have appeared at the elements of a different, colocated microphone array, i.e., "translating" measurements made at one microphone array to those hypothetically appearing at another array. Two approaches are proposed, a nonparametric method in which a fixed, low-sidelobe beamformer applied to the "source" array drives virtual sources rendered on the "target" array, and a parametric technique in which constrained beamformers are used to estimate source directions, with the sources extracted and rendered to the estimated directions. Finally, a hybrid method is proposed, which combines both approaches so that the extracted point sources and residual can be separately rendered. Experimental results using an array of 2 mm-diameter microphones and human HRTFs are reported as a simple example.
Convention Paper 7954 (Purchase now)

P19-7 Design and Optimization of High Directivity Waveguide for Vertical Array—Mario Di Cola, Audio Labs Systems - Casoli, CH, Italy; Dario Cinanni, Andrea Manzini, Tommaso Nizzoli, 18 Sound - Division of A.E.B, Srl - Cavriago, RE, Italy; Daniele Ponteggia, Studio Ponteggia - Temi, TR, Italy
Vertically arrayed loudspeaker systems have become widely used for several applications: concert sound, large scale systems, corporate events, and so on. In this kind of system the design of a proper acoustic waveguide is a key point for the system's performances. An acoustic waveguide, properly designed for this purpose, should be optimized for several features at the same time: acoustic loading properties, proper driver-throat matching, minimum internal reflection, low distortion, and, most of all, proper wavefront curvature optimization for good array-ability. An example of a practical approach to the design, dimensioning, and optimization of acoustic waveguide will be shown through loudspeaker system designing principles together with computer simulations and measured final results.
Convention Paper 7955 (Purchase now)