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Last Updated: 20060404, meiP21 - Posters: Room and Architectural Acoustics
Monday, May 22, 14:00 — 15:30
P21-1 Koch’s Snowflake: A Case Study of Sound Scattering of Fractal Surfaces—David Degos, Steven Edson, Densil Cabrera, University of Sydney - Syndey, New South Wales, Australia
Diffusion and scattering are becoming increasingly relevant in room acoustics design. The scattering performance of current passive diffusers is often restricted to a certain bandwidth due to physical constraints. One possible approach to this is to use fractal surface profiles, which have similar geometric features over a wide range of scales, and so should achieve an extended bandwidth for effective scattering. A range of acoustic panels of varying complexity, based around Koch’s Snowflake pattern, was constructed and tested using a two-dimensional pseudo-anechoic method adapted from the AES-4id-2001. This paper reports on these results and also on issues encountered in implementing the measurements.
[Poster Presentation Associated with Paper Presentation P15-1]
Convention Paper 6735 (Purchase now)
P21-2 Influence of Ray Angle of Incidence and Complex Reflection Factor on Acoustical Simulation Results (Part II)—Emad El-Saghir, Acoustic Design Ahnert Limited - Cairo, Egypt; Stefan Feistel, SDA Software Design Ahnert GmbH - Berlin, Germany
In a previous paper (Convention Paper 6171, 116th AES Convention, Berlin, Germany), it was shown that the influence of neglecting the incidence-angle dependence of absorption coefficients in a simple single-source shoebox room model was insignificant as far as simulation results are concerned. Neglecting phase shift at each reflection led, however, to a significant difference in the predicted pressure in the same model. This paper investigates the same two questions in a complicated model with several sources and a diversity of surface materials. It attempts to analytically estimate the error associated with disregarding these two issues.
[Poster Presentation Associated with Paper Presentation P15-3]
Convention Paper 6737 (Purchase now)
P21-3 Adaptive Audio Equalization of Rooms Based on a Technique of Transparent Insertion of Acoustic Probe Signals—Ariel Rocha, António Leite, Francisco Pinto, Aníbal Ferreira, University of Porto - Porto, Portugal, ATC Labs, Chatham, NJ, USA
This paper presents a new method of performing real time adaptive equalization of room acoustics in the frequency domain. The developed method obtains the frequency response of the room by means of transparent insertion of a certain number of acoustic probe signals into the main audio spectrum. The opportunities for the insertion of tones are identified by means of a spectral analysis of the audio signal and using a psychoacoustic model of frequency masking. This enhanced version of the adaptive equalizer will be explained as well as its real-time implementation on a TMS320C6713 DSP-based platform. Results of the acoustic tests and conclusions about its performance will be presented.
[Poster Presentation Associated with Paper Presentation P15-4]
Convention Paper 6738 (Purchase now)
P21-4 An Amphitheatric Hall Modal Analysis Using the Finite Element Method Compared to In Situ Measurements—Anastasia Papastefanou, Christos Sevastiadis, George Kalliris, George Papanikolaou, Aristotle University of Thessaloniki - Thessaloniki, Greece
The distribution of the low frequency room modes is important in room acoustics. The Finite Element Method (FEM) is a powerful numerical technique for analyzing the behavior of sound waves in enclosures, especially irregular ones. Also, it is the method that produces reliable results in the low frequency range where other methods like ray tracing and image source methods fail. A modal analysis is presented using the FEM in a nonrectangular, medium-sized amphitheatric hall, and we compare the calculated results with those obtained by on site measurements.
[Poster Presentation Associated with Paper Presentation P15-5]
Convention Paper 6739 (Purchase now)
P21-5 A Computer-Aided Design Method for Dimensions of a Rectangular Enclosure to Avoid Degeneracy of Standing Waves—Zhi Liu, Fan Wu, Beijing Union University - Beijing, China
A method for designing dimensions of a rectangular enclosure to avoid degeneracy of standing waves and the corresponding computer-aided design software are presented in this paper. A math model to calculate many dimensions in favor of avoiding degeneracy of standing waves is created. The similarity of the normal frequencies regarded as degeneracy is limited under a specific condition. Based on the relationship between normal frequencies and the dimensions of a rectangular enclosure, the dimensions to avoid degeneracy can be chosen. A Computer Aided Design program is also developed to identify the dimensions that can be applied in the design of a loudspeaker cabinet or room to get the best acoustic effect.
[Poster Presentation Associated with Paper Presentation P15-6]
Convention Paper 6740 (Purchase now)
P21-6 Performance Analysis of Wave Field Simulation with the Functional Transformation Method—Stefan Petrausch, Rudolf Rabenstein, University of Erlangen-Nuremberg - Erlangen, Germany
The application of the Functional Transformation Method (FTM) for the simulation of acoustical wave fields has been recently extended to complex room geometries by the usage of so-called “block-based” modeling techniques. The complete model is split into several elementary blocks with simple geometry, which are solved separately with the FTM and reconnected in the discrete system with Wave Digital Filter (WDF) principles. Concerning the performance of this algorithm, two questions arise: how much additional error is introduced compared with an all-in-one FTM solution, and how accurate are the FTM simulations compared with classical methods (e.g., digital waveguide meshes). This paper offers an answer for both questions by proving that the worst-case scenario of the proposed procedure, i.e., minimum size block models, is identical to a waveguide mesh. The complete derivation is first performed for 1-D models and then extended to 2-D wave fields, demonstrating the equivalence of minimum-size block-based FTM modeling and digital waveguide meshes.
Convention Paper 6792 (Purchase now)
P21-7 Real Time Acoustic Rendering of Complex Environments Including Diffraction and Curved Surfaces—Olivier Deille, Julien Maillard, Nicolas Noé, Centre Scientifique et Technique de Bâtiment - Saint Martin d'Hères, France; Kadi Bouatouch, Institut de Recherche en Informatique et Systèmes Aléatoires - Rennes Cedex, France; Jacques Martin, Centre Scientifique et Technique de Bâtiment - Saint Martin d'Hères, France
A solution to produce virtual sound environments based on the physical characteristics of a modeled complex volume is described. The goal is to reproduce, in real time, the sound field depending on the position of the listener and to allow some interactivity (change in material characteristics for instance). First an adaptive beam tracing algorithm is used to compute a geometrical solution between the sources and several positions inside that volume. This algorithm is not limited to polygonal faces and handles diffraction. Then, the precomputed paths, once ordered and selected, are auralized, and an adaptive artificial reverberation is used. New techniques to allow for fast and accurate rendering are detailed. The proposed approach provides accurate audio rendering on headphones or within advanced multi-user immersive environments.
[Poster Presentation Associated with Paper Presentation 15-9]
Convention Paper 6743 (Purchase now)
P21-8 Comparisons between Binaural In-Situ Recordings and Auralizations—Konca Saher, Delft University of Technology - Delft, The Netherlands; Jens Holger Rindel, Technical University Denmark - Kgs. Lyngby, Denmark; Lau Nijs, Delft University of Technology - Delft, The Netherlands
The doctoral research of “Prediction and Assessment of Acoustical Quality in Living-rooms for People with Intellectual Disabilities” at Delft University of Technology investigates, among other issues, the applicability and verification of auralization as a quality assessment tool in acoustical-architectural design. This paper deals with the comparison between binaural in-situ recordings and auralizations obtained from computer simulations. Listening tests and questionnaires were prepared from auralizations to compare with the reference binaural recordings. The difficulties in evaluation of auralization quality are discussed. The results indicate that although auralizations and binaural recordings evoke different aural perception auralization is a strong tool to assess the acoustical environment before the space is built. Two commercial programs are used for the auralizations: ODEON and CATT-Acoustics.
[Poster Presentation Associated with Paper Presentation 15-10]
Convention Paper 6744 (Purchase now)
P21-9 A Review of NFPA 72 Requirements for Emergency Communications—Michael S. Pincus, Acentech Incorporated - Cambridge, MA, USA
The National Fire Protection Association publication 72, “The National Fire Alarm Code,” is the basis for most fire codes in the United States. The latest edition, published in 2006, will have updated requirements for both sound pressure level and intelligibility relating to messages used for emergency communications. This paper describes the changes between the new edition and the previous version, published in 2002, as well as a summary of proposed changes that were not accepted. A case study will show the impact of these requirements on the design of sound system designs for a series of light rail stations in Seattle, Washington, and contrast them with subway stations in Boston, Massachusetts.
Convention Paper 6793 (Purchase now)
P21-10 Classroom Acoustics: Current and Future Criteria for the Assessment of Acoustics for Learning—Sooch San Souci, Line Guerra, Nicolas Teichner, AiA - Audition, Intelligibility, Acoustics - Boulogne, France; Dick Campbell, Bang-Campbell Associates - East Falmouth, MA, USA
Assuring that a student can hear the teacher and classmates clearly, without having to filter out excessive noise, has been a common goal of the past, but the current standards fall short of the optimum acoustic for the act of learning. Several important factors have been overlooked by the current acoustic criteria for listening while learning. For example, the actions involved in receiving new information while listening in a learning environment and and their relationshp with multiple levels of perception and concentration during the “discovery phase” of the integration of new ideas. This paper describes an approach to define distinct acoustic criteria for learning environments. Data collected from several prototype classrooms specifically built to assess criteria significance, renovation cost/value, and measurement reproducibility with acoustic criteria determined on a seat-by-seat basis will be presented.
Convention Paper 6794 (Purchase now)
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