AES London 2010
Paper Session P9

P9 - Room and Architectural Acoustics

Sunday, May 23, 09:00 — 13:00 (Room C5)
Chair: Ben Kok, Consultant - The Netherlands

P9-1 On the Air Absorption Effects in a Finite Difference Implementation of the Acoustic Diffusion Equation Model—Juan M. Navarro, San Antonio's Catholic University of Murcia - Guadalupe, Spain; José Escolano, University of Jaén - Linares, Spain; José J. Lopez, Universidad Politecnica de Valencia - Valencia, Spain
In room-acoustics modeling, the sound atmospheric attenuation is a critical phenomenon that has to be taken into account to obtain correct predictions, especially when high frequencies and large enclosures are simulated. A finite difference scheme implementation of the diffusion equation model with a mixed boundary condition is evaluated, including the air absorption within the room. This paper focuses on investigating the performance of this implementation for room-acoustics simulation. In particular, the stability condition is developed to compare the features of the solution both with and without the air absorption term. Moreover, the correct behavior of the numerical implementation has been studied comparing predicted results using different surfaces and air absorption coefficients.
Convention Paper 8021 (Purchase now)

P9-2 A Comparison of Two Diffuse Boundary Models Based on Finite Differences Schemes—José Escolano, University of Jaén - Linares, Spain; Juan M. Navarro, San Antonio's Catholic University of Murcia - Guadalupe, Spain; Damian T. Murphy, Jeremy J. Wells, University of York - York, UK; José J. López, Universidad Politécnica de Valencia - Valencia, Spain
In room acoustics, the reflection and scattering of sound waves at the boundaries strongly determines the behavior within the enclosed space itself. Therefore, the accurate simulation of the acoustic characteristics of a boundary is an important part of any room acoustics prediction model, and in particular diffuse reflections at a boundary is one of the most important properties to model correctly for an accurate and perceptually natural result. This paper presents a comparison of two simulation models for the phenomenon of diffuse reflection at a boundary: one based on introducing physical variations at the boundary itself, and another based on the use of a diffusion equation model.
Convention Paper 8022 (Purchase now)

P9-3 Considerations for the Optimal Location and Boundary Effects for Loudspeakers in an Automotive Interior—Roger Shively, Jeff Bailey, Harman International - Novi, MI, USA; Jerôme Halley, Lars Kurandt, Harman International - Karlsbad, Germany; François Malbos, Harman International - Chateau du Loir, France; Gabriel Ruiz, Harman International - Bridgend, Wales, UK; Alfred Svobodnik, Harman International - Vienna Austria
Referencing earlier work by the authors on the boundary effects in an automotive vehicle interior (AES Convention Paper 4245, May 1996) on the mid-to-high frequency timbral changes in the sound field due to the proximity to loudspeakers of reflective, semi-rigid surfaces, modeling of midsize loudspeakers in the interior of an automobile is reported on, as well as modeled results for a specific case are given.
Convention Paper 8023 (Purchase now)

P9-4 Acoustics of the Restored Petruzzelli Theater—Marco Facondini, TanAcoustics Studio - Pesaro, Italy; Daniele Ponteggia, Studio Ing. Ponteggia - Terni, Italy
Petruzzelli theater in Bari has been recently restored after the disastrous fire of 1991 had seriously damaged the building. The restoration has focused on the aesthetics and functionality of the room, in particular giving great attention to improving the acoustics of the theater. This paper reviews the acoustical design process that has been carried out using a computer model of the hall and measurements during the restoration process. Objective indexes from measurements of the renewed theater are compared with literature suggested values and with similar halls.
Convention Paper 8024 (Purchase now)

P9-5 Identification of a Room Impulse Response Using a Close-Microphone Reference Signal—Elias Kokkinis, John Mourjopoulos, University of Patras - Patras, Greece
The identification of room impulse responses is very important in many audio signal processing applications. Typical system identification methods require access to the original source signal that is seldom available in practice, while blind system identification methods require prior knowledge of the statistical properties of the source signal that, for audio applications, are not available. In this paper a new system identification method is proposed using a close-microphone reference signal, and it is shown that it accurately identifies real room impulse responses.
Convention Paper 8025 (Purchase now)

P9-6 Acoustic Impulse Response Measurement Using Speech and Music Signals—John Usher, Barcelona Media - Barcelona, Spain
Continuous measurement of room impulse responses (RIRs) in the presence of an audience has many applications for room acoustics: in-situ loudspeaker/room equalization; teleconferencing; and for architectural acoustic diagnostics. A continuous analysis of the RIR is often preferable to a single measurement, especially with non-stationary room characteristics such as from changing atmospheric or audience conditions. This paper discusses the use of adaptive filters updated according to the NLMS algorithm for fast, continuous in-situ RIR acquisition; particularly when the input signal is music or speech. We show that the dual-channel FFT (DCFFT) method has slower convergence and is less robust to colored signals such as music and speech. Data is presented comparing the NLMS and the DCFFT methods and we show that the adaptive filter approach provides RIRs with high accuracy and high robustness to background noise using music or speech signals.
Convention Paper 8026 (Purchase now)

P9-7 Evaluation of Late Reverberant Fields in Loudspeaker Rendered Virtual Rooms—Wieslaw Woszczyk, Brett Leonard, Doyuen Ko, McGill University - Montreal, Quebec, Canada
Late reverberant decay was isolated from high-resolution impulse response measured in a church that has excellent acoustics suitable for music recording. The measured multichannel impulse response (IR) was compared to two synthetic decays (SIR) built from Gaussian noise and modeled on the original IR. The synthetic decays were created to be similar to the original response in the rate of decay and spectral weighting in order to make listening comparisons between them. Four different transition points (100 ms, 200 ms, 300 ms, 400 ms) were chosen to crossfade between the original early response and the synthetic decays. Listeners auditioned the synthetic and measured rooms convolved with three anechoic monophonic sources. The results of tests conducted within immersive surround sound environment with height help to verify whether shaped random noise is a suitable substitute for late reverberation in high-resolution simulations of room acoustics.
Convention Paper 8027 (Purchase now)

P9-8 Finite Difference Room Acoustic Modeling on a General Purpose Graphics Processing Unit—Alexander Southern, University of York - York, UK, Aalto University School of Science and Technology, Aalto, Finland; Damian Murphy, University of York - York, UK; Guilherme Campos, Paulo Dias, University of Aveiro - Aveiro, Portugal
Detailed and convincing walkthrough auralizations of virtual rooms requires much processing capability. One method of reducing this requirement is to pre-calculate a data-set of room impulse responses (RIR) at locations throughout the space. Processing resources may then focus on RIR interpolation and convolution using the dataset as the virtual listening position changes in real-time. Recent work identified the suitability of wave-based models over traditional ray-based approaches for walkthrough auralization. Despite the computational saving of wave-based methods to generate the RIR dataset, processing times are still long. This paper presents a wave-based implementation for execution on a general purpose graphics processing unit. Results validate the approach and show that parallelization provides a notable acceleration.
Convention Paper 8028 (Purchase now)