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AES New York 2007
Poster Session P5

P5 - Acoustic Modeling

Friday, October 5, 2:00 pm — 3:30 pm
P5-1 Modeling of Nonlinearities in Electrodynamic LoudspeakersDelphine Bard, Göran Sandberg, Lund University - Lund, Sweden
This paper proposes a model of the nonlinearities in an electrodynamic loudspeaker based on Volterra series decomposition and taking into account the thermal effects affecting the electrical parameters when temperature increases. This model will be used to predict nonlinearities taking place in a loudspeaker and their evolution as the loudspeaker is used for a long time and/or at high power rates and its temperature increases. A temperature increase of the voice coil will cause its series resistance value to increase, therefore reducing the current flowing in the loudspeaker. This phenomenon is known as power compression.
Convention Paper 7186 (Purchase now)

P5-2 Listening Tests of the Localization Performance of Stereodipole and Ambisonic SystemsAndrea Capra, LAE Group - Parma, Italy and University of Parma, Parma, Italy; Simone Fontana, LAE Group - Parma, Italy, and Ecole Nationale Supérieure des Télécommunications, Paris, France; Fons Adriaensen, LAE Group - Parma, Italy; Angelo Farina, LAE Group - Parma, Italy, and University of Parma, Parma, Italy; Yves Grenier, Ecole Nationale Supérieure des Télécommunications - Paris, France
In order to find a possible correlation of objective parameters and subjective descriptors of the acoustics of theaters, auditoria or music halls, and perform meaningful listening tests, we need to find a reliable 3-D audio system that should give the correct perception of the distances, a good localization all around the listener, and a natural sense of realism. For this purpose a Stereo Dipole system and an Ambisonic system were installed in a listening room at La Casa Della Musica (Parma, Italy). Listening tests were carried out for evaluating the localization performances of the two systems.
Convention Paper 7187 (Purchase now)

P5-3 Round Robin Comparison of HRTF Simulation Results: Preliminary ResultsRaphaël Greff, A-Volute - Douai, France; Brian F. G. Katz, LIMSI – CNRS - Orsay, France
Variability in experimental measurement techniques of the HRTF is a concern that numerical calculation methods can hope to avoid. Numerical techniques such as the Boundary Element Method (BEM) allow for the calculation of the HRTF over the full audio spectrum from a geometrical model. While numerical calculations are not prone to the same errors as physical measurements, other problems appear that cause variations: geometry acquisition and modeling of real shapes as meshes can be performed in different ways. An on-going international round-robin study, “Club Fritz,” gathers HRTF data measured from different laboratories on a unique dummy head. This paper presents preliminary results of numerical simulation based on an acquired geometrical model of this artificial head.
Convention Paper 7188 (Purchase now)

P5-4 Simulation of Complex and Large Rooms Using a Digital Waveguide MeshJose Lopez, Technical University of Valencia - Valencia, Spain; Jose Escolano, University of Jaen - Jaen, Spain; Basilio Pueo, University of Alicante - Alicante, Spain
The Digital Waveguide Mesh (DWM) method for room acoustic simulation has been introduced in the last years to solve sound propagation problems numerically. However, the huge computer power needed in the modeling of large rooms and the complexity to incorporate realistic boundary conditions has delayed their general use, being restricted to the validation of theoretical concepts using simple and small rooms. This paper presents a complete DWM implementation that includes a serious treatment of boundary conditions, and it is able to cope with different materials in very large rooms up to reasonable frequencies. A simulation of a large building modeled with a high degree of precision has been carried out, and the obtained results are presented and analyzed in detail.
Convention Paper 7189 (Purchase now)

P5-5 The Flexible Bass AbsorberNiels W. Adelman-Larsen, Flex Acoustics - Lyngby, Denmark; Eric Thompson, Anders C. Gade, Technical University of Denmark - Lyngby, Denmark
Multipurpose concert halls face a dilemma. They host different performance types that require significantly different acoustic conditions in order to provide the best sound quality to the performers, sound engineers, and the audience. Pop and rock music contains high levels of bass sound but still require a high definition for good sound quality. The mid- and high-frequency absorption is easily regulated, but adjusting the low-frequency absorption has typically been too expensive or requires too much space to be practical for multipurpose halls. A practical solution to this dilemma has been developed. Measurements were made on a variable and mobile low-frequency absorber. The paper presents the results of prototype sound absorption measurements as well as elements of the design.
Convention Paper 7190 (Purchase now)

P5-6 The Relation between Active Radiating Factor and Frequency Responses of Loudspeaker Line Arrays – Part 2Yong Shen, Kang An, Dayi Ou, Nanjing University - Nanjing, China
Active Radiating Factor (ARF) is an important parameter for evaluating the similarity between a real loudspeaker line array and the ideal continuous line source. Our previous paper dealt with the relation between ARF of the loudspeaker line array and the Differential chart of its Frequency Responses in two distances (FRD). In this paper an improved way to estimate ARF of the loudspeaker line array by measuring on-axis frequency responses is introduced. Some further problems are discussed and experiment results are analyzed. The results may give some help to loudspeaker array designers.
Convention Paper 7191 (Purchase now)

P5-7 Time Varying Behavior of the Loudspeaker SuspensionBo Rohde Pedersen, Aalborg University - Esbjerg, Denmark; Finn Agerkvist, Technical University of Denmark - Lyngby, Denmark
The suspension part of the electrodynamic loudspeaker is often modeled as a simple linear spring with viscous damping. However, the dynamic behavior of the suspension is much more complicated than predicted by such a simple model. At higher levels the compliance becomes nonlinear and often changes during high excitation at high levels. This paper investigates how the compliance of the suspension depends on the excitation, i.e., level and frequency content. The measurements are compared with other known measurement methods of the suspension.
Convention Paper 7192 (Purchase now)

P5-8 Diffusers with Extended Frequency RangeKonstantinos Dadiotis, Jamie Angus, Trevor Cox, University of Salford - Salford, Greater Manchester, UK
Schroeder diffusers are unable to diffuse sound when all their wells radiate in phase, a phenomenon known as flat plate effect. This phenomenon appears at multiple frequencies of pf0, where p is the integer that generates the well depths and f0 the design frequency. A solution is to send the flat plate frequencies above the bandwidth of interest. For QRDs and PRDs to achieve this goal, impractically long sequences are needed. This paper presents power residue diffusers, of small length in comparison to their prime generator, as solutions to the problem. Their characteristics are investigated and their performance when applied to Schroeder diffusers is explored while modulation is used to cope with periodicity. The results confirm the expectations.
Convention Paper 7193 (Purchase now)

P5-9 Waveguide Mesh Reverberator with Internal Decay and Diffusion StructuresJonathan Abel, Patty Huang, Julius Smith III, Stanford University - Stanford, CA, USA
Loss and diffusion elements are proposed for a digital waveguide mesh reverberator. The elements described are placed in the interior of the waveguide mesh and may be viewed as modeling objects within the acoustical space. Filters at internal scattering junctions provide frequency-dependent losses and control over decay rate. One proposed design method attenuates signals according to a desired reverberation time, taking into account the local density of loss junctions. Groups of one or several adjacent scattering junctions are altered to break up propagating wavefronts, thereby increasing diffusion. A configuration that includes these internal elements offers more flexibility in tailoring the reverberant impulse response than the common waveguide mesh construction where loss and diffusion elements are uniformly arranged solely at the boundaries. Finally, such interior decay and diffusion elements are ideally suited for use with closed waveguide structures having no boundaries, such as spherical or toroidal meshes, or meshes formed by connecting the edges or surfaces of two or more meshes.
Convention Paper 7194 (Purchase now)

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