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AES Amsterdam 2008
Room and Architectural Acoustics & Sound Reinforcement
Paper Session P18
Monday, May 19, 12:30 — 17:00
Chair: Jan Voetmann, DELTA Acoustics - Hoersholm, Denmark
P18-1 Diffusing Boundary Implementations in the 2-D Digital Waveguide Mesh—Simon Shelley, Technische Universiteit Eindhoven - Eindhoven, The Netherlands; Damian Murphy, York University - Heslington, York, UK
The digital waveguide mesh is a wave-based time-domain approach to the simulation of sound wave propagation in an acoustic system. The implementation of diffuse reflection is an important consideration in such an application, as the presence of diffuse reflection has a significant effect on an acoustic environment. The scattering effect of diffuse boundaries on reflected sounds, both in simulation and the real world, can be described using a technique that results in the formulation of frequency dependent diffusion coefficients. In this paper a number of different approaches to modeling diffuse reflection in a 2-D digital waveguide mesh are presented as well as a detailed analysis and comparison of the local scattering effect of the diffuse boundary models using this technique.
Convention Paper 7428 (Purchase now)
P18-2 RenderAIR—Room Acoustics Simulation Using a Hybrid Digital Waveguide Mesh—Damian Murphy, Mark Beeson, University of York - Heslington, York, UK; Simon Shelley, Eindhoven University of Technology - Eindhoven, The Netherlands; Alex Southern, Alastair Moore, University of York - Heslington, York, UK
The digital waveguide mesh (DWM) is a numerical simulation technique used to model signal propagation through a regular grid of spatio-temporal sampling points, and has been demonstrated as appropriate for modeling the acoustics of an enclosed space, particularly at low frequencies. The RenderAIR DWM application allows intuitive definition of parameters associated with geometry, boundary surface, and source/receiver parameters required to generate spatially encoded Room Impulse Responses (RIRs). In this paper the expectations and limitations of DWM-based room acoustics modeling are explored through the use of the RenderAIR application in a number of situations. ISO3382 metrics are used as the main benchmark for the results obtained, which compare well with both real-world measurements and more traditional geometric acoustic approaches.
Convention Paper 7429 (Purchase now)
P18-3 Volumetric Diffusers—Richard Hughes, Jamie A. S. Angus, Trevor Cox, Olga Umnova, University of Salford - Salford, Greater Manchester, UK
Although many types of diffusers have been proposed, they are predominantly surface treatment. This paper places the diffuser in the volume of the room rather than on the surfaces, forming a volume-based diffuser. In particular, we examine suitable sequences for their implementation. We also consider suitable metric’s to evaluate their performance. At first single layer volumetric diffusers are examined, and then multi-layer volumetric diffusers are investigated. In particular, the effects of varying the spacing, and number of layers, is more closely examined. The Boundary Element Method (BEM) model is used to gain accurate predictions of the diffuser’s performance. Finally, we demonstrate a diffusion structure that has a similar performance to that of a Primitive Root Diffuser (PRD).
Convention Paper 7432 (Purchase now)
P18-4 Commercial Low Frequency Absorbers—A Comparative Study—Gabriel Hauser, Dirk Noy, Walters-Storyk Design Group - Basel, Switzerland; John Storyk, Walters-Storyk Design Group - Highland, NY, USA
This paper ties in to a previous Convention Paper by the same authors (AES 115th Convention, 2003, #5944) and presents a current set of commercially available passive and active low frequency absorbing devices. One item in particular is of an experimental nature—a wood box loaded with conventional membrane loudspeakers. These are not connected to an amplifier, but to a variety of different passive electronics networks (parallel, serial). Reproducible acoustical measurements have been taken in a completely untreated rectangular concrete room, sequentially with and without a total of eight different absorbing devices. Results are compared and conclusions are presented.
Convention Paper 7431 (Purchase now)
P18-5 Modeling Frequency-Dependent Boundaries as Digital Impedance Filters in FDTD and K-DWM Room Acoustic Simulation—Konrad Kowalczyk, Maarten van Walstijn, Queen's University Belfast - Belfast, Northern Ireland, UK
This paper presents a new method for modeling frequency-dependent boundaries in finite difference time domain (FDTD) and Kirchhoff variable digital waveguide mesh (K-DWM) room acoustics simulations. The proposed approach allows direct incorporation of a digital impedance filter (DIF) in the multi-dimensional (i.e., 2-D or 3-D) FDTD boundary model of a locally reacting surface. An explicit boundary update equation is obtained by carefully constructing a suitable recursive formulation. The method is analyzed in terms of pressure wave reflectance for different wall impedance filters and angles of incidence. Results obtained from numerical experiments confirm the high accuracy of the proposed digital impedance filter boundary model, the reflectance of which closely matches locally reacting surface (LRS) theory. Furthermore, a numerical boundary analysis (NBA) formula is provided as a technique for analytic evaluation of the numerical reflectance of the proposed digital impedance filter boundary formulation.
Winner of the Student Paper Award
Convention Paper 7430 (Purchase now)
P18-6 Loudspeaker Time Alignment Using Live Sound Measurements—Wolfgang Ahnert, Stefan Feistel, Thorsten Maier, Alexandru Radu Miron, Ahnert Feistel Media Group - Berlin, Germany
The authors previously introduced the measurement software EASERA SysTune, which can be used for measurements with live music and speech signals. In this paper we discuss specifically the use of real-time measurements for the time alignment of loudspeaker arrays and distributed systems and for the optimal adjustment of their phase relationships. Being capable of deriving impulse responses of up to 12 seconds length, the measuring process with EASERA SysTune is simpler and more accurate as the real-time function provides a more immediate view on the tuning process. Because measurements can be performed with standard stimulus signals as well as with external speech and music signals, fine-tuning loudspeaker settings becomes possible even during the rehearsal time of the musicians. Required measurement conditions and limitations are given.
Convention Paper 7433 (Purchase now)
P18-7 INR as an Estimator for the Decay Range of Room Acoustic Impulse Responses—Constant Hak, Eindhoven University of Technology - Eindhoven, The Netherlands; Jan Hak, Acoustics Engineering - Boxmeer, The Netherlands; Remy Wenmaekers, Level Acoustics - Eindhoven, The Netherlands
A room acoustic impulse response can be used to derive the reverberation time and other parameters. To this end a certain minimum energy decay range or effective signal to noise ratio is required, which relates to the difference between the integrated signal level and the noise level. An impulse response parameter called INR is presented as an estimator for the decay range and shown to be a useful qualifier in practical measurements.
Convention Paper 7434 (Purchase now)
P18-8 Musical-Inspired Features for Automatic Sound Classification in Digital Hearing Aids—Pedro Vera-Candeas, Francisco J. Cañadas-Quesada, University of Jaén - Linares, Jaén, Spain; Enrique Alexandre, Manuel Rosa, University of Alcalá - Alcalá, Spain
This paper proposes the use of some musical-inspired features for the automatic classification of sounds in digital hearing aids. This kind of application is characterized by very strong constraints in terms of computational complexity. The proposed features are based on fundamental frequency detection and exhibit a low computational complexity while providing good results in terms of probability of correct classification. The performance of the system will be tested using a 1-NN classifier, the goal being to distinguish among speech, noise, and music. For the experiments a sound database, obtained using a hearing aid simulator, will be used.
Convention Paper 7435 (Purchase now)
P18-9 Assessing the Potential Intelligibility of Assistive Audio Systems for the Hard of Hearing and Other Users—Peter Mapp, Peter Mapp Associates - Colchester, Essex, UK
Around 14% of the European population suffer from a noticeable degree of hearing loss and would benefit from some form of hearing assistance or deaf aid. Recent DDA legislation and requirements mean that many more hearing assistive systems are being installed—yet there is evidence to suggest that many of these systems fail to perform adequately and provide the benefit expected. This paper reports on the results of some trial acoustic performance testing of such systems. In particular the effects of system microphone type, distance, and location are shown to have a significant effect on the resultant performance. The potential of using the Sound Transmission Index (STI) and in particular STIPa, for carrying out installation surveys has been investigated, and a number of practical problems are highlighted. The requirements for a suitable acoustic test source to mimic a human talker are discussed as is the need to the need to adequately assess the effects of both reverberation and noise. The findings discussed in the paper are also relevant to the installation and testing of classroom “sound field” systems and also boardroom type reinforcement systems and conferencing / teleconferencing systems.
Convention Paper 7436 (Purchase now)
Last Updated: 20080612, tendeloo