Sound Scattering by a Hard Half-Plane: Experimental Evidence of the Edge-Diffracted Wave

Ouis, Djamel

doi:10.1006/jsvi.2001.4003

Cited by 3 publications

(4 citation statements)

References 19 publications

(9 reference statements)

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“…The signal recorded by the microphone shows clearly the presence of the direct pulse signal emitted by the loudspeaker, which takes the shortest time to reach the microphone, and shortly afterwards the signal scattered by the edge of the flat screen. The experimentally determined signal agrees well with the theoretical prediction, both in the time domain and in the frequency domain (Ouis, 2002). An important motivation for the use of transient waves in acoustical studies is the importance that the impulse response has for extracting useful information about the system under investigation.…”

Section: Diffraction Of Sound Around Obstacles and Screenssupporting

confidence: 80%

Acoustical parameters used for the subjective assessment of musical performance spaces

Ouis

2006

Journal of New Music Research

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The problem of evaluating the subjective acoustical quality of a performance space through studying the value of measurable acoustical parameters is yet to be fully solved. As a contribution to its solution this paper aims to determine whether any relationships exist between the various acoustic parameters most often considered. The acoustical parameters that are topical for this study are in the number of three. The first of these parameters is the Inter-Aural Cross-Correlation Coefficient (IACC), which is a measure of the diffuseness of the sound field in the room. Then the Early Lateral Energy Fraction (ELEF), or a related measure, the Spaciousness (S), is used for estimating the relative amount of early sound energy reaching the listener from lateral incidence. And lastly the Initial Time Delay Gap (ITDG), which is a temporal factor and an indicator of the rapidity of early echoes for contributing to the early signal build-up at following the direct signal. For the evaluation of these parameters, the impulse response, IR, of the investigated enclosure is necessary. In room acoustical contexts the IR of a room is defined as the response that would be recorded by a microphone in response to a sharp and intense sound signal emitted within the enclosure. For the sake of calculation convenience a medium sized rectangular room is considered in this study and which represents a coarse approximation to a small performance hall. The theoretical model used for evaluating the IR makes a combination of the image sources method for wave reflections at the hard surfaces, and an exact model accounting for the diffraction of waves at the corners of the balconies. Furthermore, and in view of a more realistic determination of, especially the IACC, the phenomenon of sound scattering by the head of the listener is also taken into account. The variation of the value of the acoustic parameters with the position within the room at a constant height position for a presumed listener's ears is then presented in threedimensional plots. Furthermore, psychoacoustical experiments have shown that the early part of the IR is decisive for the subjective assessment of performance spaces, and further, that the low frequency components of a signal have an important contribution to the feeling of spaciousness. Therefore, a low frequency filtering of the early part of the IR was accomplished for the needs of this study. As a completion to this study, an attempt has also been made toward enhancing the existence of some possible correlation between the various parameters investigated herein. As a result, simple relations may in fact be established between these parameters, and the usefulness of these relationships may find applications in subjective room acoustical assessments for instance for estimating one of these parameters, when inaccessible, from knowing the value of any of the two other ones.

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Section: Diffraction Of Sound Around Obstacles and Screenssupporting

confidence: 80%

Acoustical parameters used for the subjective assessment of musical performance spaces

Ouis

2006

Journal of New Music Research

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“…Menounou and You used a single source position with multiple receivers but avoided positions near the reflection and shadow boundaries, and also provided only time-domain comparisons. Ouis [15] presented time and frequency-domain comparisons of measured and simulated diffraction from a thin aluminum plate, also using Medwin's BTM formulation, but only for two source/receiver combinations.…”

Section: Diffraction Measurementsmentioning

confidence: 99%

“…For example, Ouis [15] used a simplified version of the Biot-Tolstoy method. Tsingos et al [17] applied the Uniform Theory of Diffraction (UTD) with the beam-tracing modeling method, and Sakurai and Nagata [20] simulated diffraction with the Kirchhoff approximation.…”

Section: Diffraction Modelingmentioning

confidence: 99%

Measurement and modeling of diffraction from an edge of a thin panel

Lokki¹,

Pulkki

Calamia

2008

Applied Acoustics

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“…An obvious test case for diffraction modeling is noise barrier modeling, for which numerous evaluations have been presented. Two examples which used similar modeling techniques as in room acoustics are [7,8]. Accurate measurements are required for the evaluation, but such measurements are very time consuming.…”

Section: Introductionmentioning

confidence: 99%

Open Measurements of Edge Diffraction from a Noise Barrier Scale Model

2011

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Until today, all known simulation methods for the wave phenomenon of edge diffraction are just approximations, based on either Geometrical Acoustics or the numerical solving of the wave equation. Although these methods work fine for simple test scenarios and a certain frequency range, they fail to simulate the effect of diffraction in its whole complexity. This leads to false predictions especially for more complex geometries where the influence of multiple wave diffraction and sound scattering has to be taken into account as well. Consequently, huge effort is currently put into the development of improved simulation methods. Here, a basic need is an all-embracing validation of simulation results, which also includes the comparison with realworld measurements. Unfortunately, there is a lack of such data which is the reason why the Institute of Technical Acoustics (ITA), RWTH Aachen University, Germany, and the Centre for Quantifiable Quality of Service in Communication Systems (Q2S), NTNU Trondheim, Norway, have started an initiative called openMeasurements, which is aimed to be an internet platform for free acoustic measurement data of any kind, together with their respective simulation models (CAD-model, detailed information on sources and receivers, material data) and helpful tools. As initial step, various measurement series of a scaled-down model of a noise barrier were carried out. These series aim to give researches, developers, and common application users, the possibility to thoroughly test their prediction models of edge diffraction. The measurements were carried out in a full anechoic chamber and a turntable was used to rotate the scale-model during the measurements in steps of one degree. The scale-model was constructed with a changeable ground layer in order to massively influence the object's acoustical properties and, thus, create measurement datasets that considerably differ. Here, datasets for five different ground layers were obtained: 3 absorbers, 1 rigid surface and 1 self-constructed skylinediffuser. A skyline diffuser was chosen as it is a well reproducible geometrical pattern, which enables a simulation of sound scattering in two ways: stochastic and deterministic. In this contribution, detailed information on the measurement setup is given and measurement procedures are described thoroughly. Measurement uncertainties are briefly discussed and first comparisons with simulations are presented. All measurements together with geometrical models of the scale-model (with/without diffuser), detailed information on sources and receivers, material data (absorption-and scattering coefficients) and useful Matlab tools are freely available for download (www.openmeasurements.net).

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Sound Scattering by a Hard Half-Plane: Experimental Evidence of the Edge-Diffracted Wave

Cited by 3 publications

References 19 publications

Acoustical parameters used for the subjective assessment of musical performance spaces

Acoustical parameters used for the subjective assessment of musical performance spaces

Measurement and modeling of diffraction from an edge of a thin panel

Open Measurements of Edge Diffraction from a Noise Barrier Scale Model

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