Last Updated: 20050401, meiTuesday, May 31, 11:30 — 13:00
Z10-1 Definition of Materials Properties in the Acoustical Model Calibration—Konca Saher, Lau Nijs, Marinus van der Voorden, Technical University Delft - Delft, The Netherlands
There are now many commercially available computer programs for predicting acoustics of rooms. All of these computer programs work on the basis of the definition of a room’s geometry, material properties (mainly the absorption and diffusion characteristics), and definition of the sound source. The results of the calculation are then strongly dependent upon the approximation of these parameters. In this paper difficulties in the process are indicated and then a methodology for the calibration procedure for ray-tracing software is suggested. The proposed methodology consists of three main items: absorption-calculator charts, diffusion estimation, and G-RT graphs. The mentioned issues of the calibration methodology are briefly discussed and examined by a case study.
Convention Paper 6496 (Purchase now)
Z10-2 Acoustical Modeling Using a Russian Roulette Strategy—Bill Kapralos, Michael R. Jenkin, York University - Toronto, Canada; Evangelos Milios, Dalhousie University - Halifax, Nova Scotia, Canada, and York University, Toronto, Canada
One problem with geometric (ray) based acoustical modeling approaches is handling the potentially large number of interactions between a propagating acoustic ray and objects/surfaces it may encounter. Typical solutions to modeling these interactions include emitting several "new" rays at each interaction point. Unfortunately this type of approach is computationally expensive for all but the simplest environments. Rather than deterministically following these generated rays, probabilistic techniques such as Russian Roulette can be applied instead. Russian Roulette ensures the path length of each acoustic ray is kept at a manageable size yet allows for arbitrary sized paths to be explored. Here we investigate the relative performance between Russian Roulette and deterministic acoustical modeling for purely diffuse environments using the sonel mapping method.
Convention Paper 6497 (Purchase now)
Z10-3 Computation of Directional Impulse Responses in Rooms for Better Auralization—Jean-Jacques Embrechts, Nicolas Werner, Stéphane Lesoinne, University of Liege - Liege, Belgium
Auralization in room acoustics is created by the convolution of an anechoic audio signal with the RIR (room impulse response), either computed or measured at the receiver location. When headsets are used for reproduction, the same auralized signal is often sent to both ears, for simplicity. This paper addresses the computation of directional impulse responses by a sound ray program. These responses are used in the convolution process in combination with HRTFs to simulate not only the room reverberation but also the angular location of all sound contributions to the receiver. Computational problems include the separate treatment of specular and diffuse reflections and the compromise between computing time, the number, and the accuracy of directional RIRs.
Convention Paper 6498 (Purchase now)
Z10-4 Estimation of Reverberation Time without Test Signals—José Vieira, Universidade de Aveiro / IEETA - Aviero, Portugal
The reverberation time of a room affects the performance of several systems such as sound localizers, hearing aids, and telephony. However, the impact of long reverberation time on this systems can be reduced, if the strategies of the algorithms are adapted according to the value of the reverberation time. Performing the measurement of the reverberation time using a traditional approach with a controlled excitation, it is not always possible in hearing-aid devices. This paper proposes a method to measure the reverberation time by proper analysis of the captured sounds, such as voice. The algorithm detects the segments of the signal where the sound energy decreases and uses these segments to estimate the reverberation time.
Convention Paper 6499 (Purchase now)
Z10-5 Auralization of Simulated Impulse Responses in Slow Motion—Tapio Lokki, Helsinki University of Technology - Espoo, Finland
A novel auralization method, in which the propagation speed of sound is slowed down, is presented. The auralization in slow motion enables the study of details of simulated impulse responses, such as spatial distribution of early reflections and the spectrum of each reflection, in great detail. It is more intuitive than the visualization of room acoustics modeling results, and it gives more information than conventional binaural or multichannel auralization of impulse responses. The proposed method can be applied in room acoustics design as well as in teaching of room acoustics.
Convention Paper 6500 (Purchase now)
Z10-6 An Improved Adaptive Room Equalization in the Frequency Domain—Antonio Leite, INESC Porto - Porto, Portugal; Aníbal Ferreira, University of Porto, INESC Porto - Porto, Portugal
This paper presents several improvements that have been introduced on the design and operation of an adaptive 20-band room equalizer. The equalizer is implemented on a TMS320C6711 DSP platform and performs fast FIR filtering in the frequency domain. In order to reach fast adaptation to time-varying acoustic conditions, several adaptation rules operating in the frequency domain have been evaluated and the impact of a frequency-varying step-size parameter on the convergence rate has been studied. These results will be presented along with ideas and plans for future developments.
Convention Paper 6501 (Purchase now)
Z10-7 Requirements to Acoustically Prepare a Recording Studio—José Luis Molero Milán, La Salle Bonanova University - Barcelona, Spain
Sound recording and listening rely mainly on the acoustic characteristics of the environment. Places built for specific applications (music recording, conferences or concert rooms) must have the right acoustic quality. Listening and acoustic signals in a room generally are affected by different elements inherent to the room, such as reverberation, echoes, and resonance or the lack of them, and the sources sound coverage. All these elements interact with the main signal and affect an original acoustic wave. This paper describes a new method to evaluate acoustic rooms that is applicable to recording and control rooms but not to concert or lecture halls.
Convention Paper 6502 (Purchase now)
Z10-8 Acoustic Modeling of Ancient Odeion of Thessaloniki—Christos Zarras, Christos Sevastiadis, George Kalliris, George Papanikolaou, Aristotle University of Thessaloniki - Thessaloniki, Greece
An interesting part of the remaining ancient Greek buildings is that of the ancient odea. One of them is the odeion of Thessaloniki, which is at the ancient market (agora) in the center of the city. It is a small, amphitheatric hall whose exact shape and acoustical characteristics are not known, since its roof is not preserved. Acoustical measurements and an accurate a model of it, as it is today (uncovered) is presented. Moreover, the acoustical characteristics of the roofed hall are estimated, using certain types of roofs.
Convention Paper 6503 (Purchase now)
Z10-9 An Application for a Digitally Steerable Array—Michael Pincus, Acentech Inc. - Cambridge, MA, USA
While the theory and practical applications of line array loudspeaker systems are well known, cost-effective digital signal processors have enabled new systems to feature beams that can be steered and adjusted. This in turn has allowed the use of these systems in multipurpose spaces. This paper will demonstrate an example of how an active line array system can be used in an auditorium featuring a moveable partition.
Convention Paper 6504 (Purchase now)
Z10-10 Digital Frequency Shifting for Electroacoustic Feedback Suppression—Carlos Vila Deutschbein, Enginyeria I Arquitechtura La Salle - Barcelona, Spain
In the field of electroacoustic installations, several more or less sophisticated methods may be used to avoid annoying feedback "howl" and boost the potential acoustic gain (PAG) by a few dB. This paper discusses the use of a digital frequency shifter instead of more popular narrow-band filtering techniques. The device has been implemented using a readily available programmable DSP platform and its efficiency has been proven by measurements in various environments.
Convention Paper 6505 (Purchase now)
Z10-11 High-Power Amplifier With Direct Three-Phase 400-V Power Supply—Vladimir Filevski, Broadcasting Council of Macedonia - Skopje, Macedonia
The proposed amplifier has a direct three-phase 400-V power supply that consists only of diodes and uses neither filtering capacitors nor a transformer. This amplifier consists of three modules. The first module is a conventional Class-D digital audio amplifier, which can work on high voltage supply. The second module is a simple three-phase full-wave diode rectifier which rectifies alternating voltage of a 400-V three-phase line system. The third module is a negative feedback system that nearly eliminates the ripple voltage in the output signal. With the help of this negative feedback, the first module (conventional class-D amplifier) actually behaves as it has power supply with the voltage equal to the pure DC component of the rectified three-phase voltage (about 280 VDC).
Convention Paper 6506 (Purchase now)
©2005 Audio Engineering Society, Inc.