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Papers by Panos Economou
The definition of Reverberation Time (RT) is based on a phenomenon which is far more complex than... more The definition of Reverberation Time (RT) is based on a phenomenon which is far more complex than the definition is able to explain. Sabine in his effort to solve an engineering problem at first tackled the problem empirically and then tried to justify the findings of his empirical work within a theoretical framework by the use of many assumptions. Ever since then, the acoustical community tried to better understand the parameter described as RT confined within the original concept of Sabine which begins to converge on Sabine's idea of RT above the Schroeder frequency. This paper tries to redefine the way we investigate this acoustical phenomenon without Sabine's assumptions which are: (a) That an isotropic and homogeneous acoustical field exists within a room, (b) developed by sound reflections only, (c) due to plane wave sound propagation, (d) RT can be calculated using the borrowed concept of the Mean Free Path from particle physics and optics, (e) the use of sound absorption coefficients and (f) energy summation. This paper studies room modal decay using (i) spherical wave propagation, (ii) surface impedance (iii) a sound field formed by sound reflections and diffractions and (iv) sound pressure summation preserving wave front phase information.
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The seat dip effect is considered to be one of the intractable acoustical phenomena in room acous... more The seat dip effect is considered to be one of the intractable acoustical phenomena in room acous-tical simulations. This phenomenon is mainly due to edge sound diffraction and scattering. Wave Based Geometrical Acoustics (WBGA), which originates from the image source method, spherical wave propagation, impedance discontinuities and sound pressure summation, accounts for wave phenomena such as reflection from planes, diffraction from edges, refraction due to strati-fication of mediums to mention a few. By applying WBGA, we demonstrate that the seat dip effect can be accurately calculated and predicted. This paper compares results of the seat dip effect calculated using WBGA with published and measured data.
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Geometrical acoustics, using plane wave propagation and sound absorption coefficients, fail to ca... more Geometrical acoustics, using plane wave propagation and sound absorption coefficients, fail to calculate room resonances. Usually such wave phenomena are being calculated with numerical methods such as Finite Element Method or similar which are computationally heavy. The WBGA, which is based on the image source method, spherical wave propagation, impedance discontinu-ities and sound pressure summation, can accurately simulate room resonances both in the frequency and spatial domain. In this paper we present calculation results of room resonances using the WBGA compared to published data.
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Bookmarks Related papers MentionsView impact
Ray-tracing software, which uses ISO 9613-2 to compute outdoor propagation, is practical, and has... more Ray-tracing software, which uses ISO 9613-2 to compute outdoor propagation, is practical, and has been used successfully for design. However, serious doubts exist regarding the accuracy of some of the various empirical algorithms used, such as algorithms for ground effects and reflections, source height, reflections by objects, and ground cover. Further, 9613-2 has no algorithms for turbulence, phase, and wave length (except barrier diffraction). New wave-based image-source software (Olive Tree Lab-Terrain by PEMARD) uses theoretically accurate 3-dimensional algorithms that agree more closely with measurements than 9613. It takes into account reflections from finite impedance surfaces and finite-sized objects, applying Fresnel zone corrections as well as diffractions of unlimited orders from edges. The new software also calculates constructive and destructive interferences that are not possible with simpler algorithms, including 9613-2. Full-wave solutions (such as Greens Function-Parabolic Equation), which can also calculate wave-length effects, are usually too computation-intensive for design. The new software is computationally practical for the very large number of sources and sub-sources that are typically modeled during design. This paper compares results of calculations using selected advanced calculation algorithms from OTL-Terrain with measurements and those from 9613-2 both as a function of frequency and distance.
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DAGA 2014
The path from a noise source to a receiver involves complicated mechanisms such as diffractions a... more The path from a noise source to a receiver involves complicated mechanisms such as diffractions and reflections from ob-
stacles, ground and material properties, as well as meteorological conditions. In this paper, we present the methodology
applied by P.E. Mediterranean Acoustics Research & Development for outdoor sound propagation applying advanced
calculation methods for prediction and simulation purposes in a software application. The methodology makes use of
the image source method combined with visibility tracing techniques to implement a novel method of multiple path-
detection, taking into account reflections from finite impedance surfaces and finite-sized objects applying Fresnel zone
corrections as well as diffractions of unlimited orders from edges. These advanced methods are no longer used only in
the laboratory but are now available to engineers in the field, making theory available in practice. Some examples are
also presented.
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Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
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Despite the rapid development in acoustics calculation software during the last couple of decades... more Despite the rapid development in acoustics calculation software during the last couple of decades, such advances have not been achieved uniformly. Various demands in different disciplines have shifted the focus to a number of different aspects of the calculations. Methods in game development have focused on speed and optimized calculation times to achieve interactive sound rendering, whilst engineering methods have concentrated in achieving accuracy for reliable predictions. This paper presents a flexible, expandable and adjustable framework for the development of fast and accurate acoustics calculations both for game development and engineering purposes. It decomposes the process of acoustic calculations for 3D environments into distinct calculation steps and allows third party users to adjust calculation methodologies according to their needs.
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Acta Acustica united with Acustica, 2013
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Until recently geometrical acoustics has been considered an approximate method of calculating the... more Until recently geometrical acoustics has been considered an approximate method of calculating the sound field within a 3D environment because of certain limitations in existing methods. Geometrical acoustics mostly refers to the use of ray tracing and image sources. Ray tracing is a pure energetic method, while the image source method, despite calculating complex sound pressures and theoretically representing a solution to the wave equation, has certain limitations. One of the limitations found in most of the image source implementations is the use of plane wave reflection coefficient and absorption coefficients, a fact that prohibited image sources to be an exact solution of the wave equation. In this paper we extend the image source method, using spherical wave reflection and diffraction coefficients as well as complex surface impedance. We compare the results of the calculations with published data and we conclude that the use of spherical wave coefficients and complex impedance can improve room acoustics predictions.
Bookmarks Related papers MentionsView impact
Conference Presentations by Panos Economou
Calculation of noise propagation from wind turbines is complex, and large variations of sound imm... more Calculation of noise propagation from wind turbines is complex, and large variations of sound immission levels are commonly observed at the same wind speed. These variations are influenced by sound emission (aerodynamic noise), but also by meteorological parameters such as temperature gradient, wind speed profile, wind direction, and turbulences. Commonly used models (ISO 9613-2 and Nord2000 for example) generally predict the average sound pressure levels adequately under downwind conditions, but often fail to predict noise levels in upwind conditions. In this paper we present the results of a collaborative research between SIXENSE Environment (ex SOLDATA Acoustic) and P.E Mediterranean Acoustics Research & Development (PEMARD), using on site experience on more than 350 French windfarms, and Olive Tree Lab-Suite v4.0 software which uses wave based geometrical acoustics to calculate sound propagation, including atmospheric refraction. The goal is to combine both approaches and introduce and test key parameters for wind turbine noise prediction. Calculation results are compared to long term noise & meteorological measurements. A good correlation is shown between calculation and measurements even in case of complex meteorological situations.
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Bookmarks Related papers MentionsView impact
Talks by Panos Economou
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The definition of Reverberation Time (RT) is based on a phenomenon which is far more complex than... more The definition of Reverberation Time (RT) is based on a phenomenon which is far more complex than the definition is able to explain. Sabine in his effort to solve an engineering problem at first tackled the problem empirically and then tried to justify the findings of his empirical work within a theoretical framework by the use of many assumptions. Ever since then, the acoustical community tried to better understand the parameter described as RT confined within the original concept of Sabine which begins to converge on Sabine's idea of RT above the Schroeder frequency. This paper tries to redefine the way we investigate this acoustical phenomenon without Sabine's assumptions which are: (a) That an isotropic and homogeneous acoustical field exists within a room, (b) developed by sound reflections only, (c) due to plane wave sound propagation, (d) RT can be calculated using the borrowed concept of the Mean Free Path from particle physics and optics, (e) the use of sound absorption coefficients and (f) energy summation. This paper studies room modal decay using (i) spherical wave propagation, (ii) surface impedance (iii) a sound field formed by sound reflections and diffractions and (iv) sound pressure summation preserving wave front phase information.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The seat dip effect is considered to be one of the intractable acoustical phenomena in room acous... more The seat dip effect is considered to be one of the intractable acoustical phenomena in room acous-tical simulations. This phenomenon is mainly due to edge sound diffraction and scattering. Wave Based Geometrical Acoustics (WBGA), which originates from the image source method, spherical wave propagation, impedance discontinuities and sound pressure summation, accounts for wave phenomena such as reflection from planes, diffraction from edges, refraction due to strati-fication of mediums to mention a few. By applying WBGA, we demonstrate that the seat dip effect can be accurately calculated and predicted. This paper compares results of the seat dip effect calculated using WBGA with published and measured data.
Bookmarks Related papers MentionsView impact
Geometrical acoustics, using plane wave propagation and sound absorption coefficients, fail to ca... more Geometrical acoustics, using plane wave propagation and sound absorption coefficients, fail to calculate room resonances. Usually such wave phenomena are being calculated with numerical methods such as Finite Element Method or similar which are computationally heavy. The WBGA, which is based on the image source method, spherical wave propagation, impedance discontinu-ities and sound pressure summation, can accurately simulate room resonances both in the frequency and spatial domain. In this paper we present calculation results of room resonances using the WBGA compared to published data.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Ray-tracing software, which uses ISO 9613-2 to compute outdoor propagation, is practical, and has... more Ray-tracing software, which uses ISO 9613-2 to compute outdoor propagation, is practical, and has been used successfully for design. However, serious doubts exist regarding the accuracy of some of the various empirical algorithms used, such as algorithms for ground effects and reflections, source height, reflections by objects, and ground cover. Further, 9613-2 has no algorithms for turbulence, phase, and wave length (except barrier diffraction). New wave-based image-source software (Olive Tree Lab-Terrain by PEMARD) uses theoretically accurate 3-dimensional algorithms that agree more closely with measurements than 9613. It takes into account reflections from finite impedance surfaces and finite-sized objects, applying Fresnel zone corrections as well as diffractions of unlimited orders from edges. The new software also calculates constructive and destructive interferences that are not possible with simpler algorithms, including 9613-2. Full-wave solutions (such as Greens Function-Parabolic Equation), which can also calculate wave-length effects, are usually too computation-intensive for design. The new software is computationally practical for the very large number of sources and sub-sources that are typically modeled during design. This paper compares results of calculations using selected advanced calculation algorithms from OTL-Terrain with measurements and those from 9613-2 both as a function of frequency and distance.
Bookmarks Related papers MentionsView impact
DAGA 2014
The path from a noise source to a receiver involves complicated mechanisms such as diffractions a... more The path from a noise source to a receiver involves complicated mechanisms such as diffractions and reflections from ob-
stacles, ground and material properties, as well as meteorological conditions. In this paper, we present the methodology
applied by P.E. Mediterranean Acoustics Research & Development for outdoor sound propagation applying advanced
calculation methods for prediction and simulation purposes in a software application. The methodology makes use of
the image source method combined with visibility tracing techniques to implement a novel method of multiple path-
detection, taking into account reflections from finite impedance surfaces and finite-sized objects applying Fresnel zone
corrections as well as diffractions of unlimited orders from edges. These advanced methods are no longer used only in
the laboratory but are now available to engineers in the field, making theory available in practice. Some examples are
also presented.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Despite the rapid development in acoustics calculation software during the last couple of decades... more Despite the rapid development in acoustics calculation software during the last couple of decades, such advances have not been achieved uniformly. Various demands in different disciplines have shifted the focus to a number of different aspects of the calculations. Methods in game development have focused on speed and optimized calculation times to achieve interactive sound rendering, whilst engineering methods have concentrated in achieving accuracy for reliable predictions. This paper presents a flexible, expandable and adjustable framework for the development of fast and accurate acoustics calculations both for game development and engineering purposes. It decomposes the process of acoustic calculations for 3D environments into distinct calculation steps and allows third party users to adjust calculation methodologies according to their needs.
Bookmarks Related papers MentionsView impact
Acta Acustica united with Acustica, 2013
Bookmarks Related papers MentionsView impact
Until recently geometrical acoustics has been considered an approximate method of calculating the... more Until recently geometrical acoustics has been considered an approximate method of calculating the sound field within a 3D environment because of certain limitations in existing methods. Geometrical acoustics mostly refers to the use of ray tracing and image sources. Ray tracing is a pure energetic method, while the image source method, despite calculating complex sound pressures and theoretically representing a solution to the wave equation, has certain limitations. One of the limitations found in most of the image source implementations is the use of plane wave reflection coefficient and absorption coefficients, a fact that prohibited image sources to be an exact solution of the wave equation. In this paper we extend the image source method, using spherical wave reflection and diffraction coefficients as well as complex surface impedance. We compare the results of the calculations with published data and we conclude that the use of spherical wave coefficients and complex impedance can improve room acoustics predictions.
Bookmarks Related papers MentionsView impact
Calculation of noise propagation from wind turbines is complex, and large variations of sound imm... more Calculation of noise propagation from wind turbines is complex, and large variations of sound immission levels are commonly observed at the same wind speed. These variations are influenced by sound emission (aerodynamic noise), but also by meteorological parameters such as temperature gradient, wind speed profile, wind direction, and turbulences. Commonly used models (ISO 9613-2 and Nord2000 for example) generally predict the average sound pressure levels adequately under downwind conditions, but often fail to predict noise levels in upwind conditions. In this paper we present the results of a collaborative research between SIXENSE Environment (ex SOLDATA Acoustic) and P.E Mediterranean Acoustics Research & Development (PEMARD), using on site experience on more than 350 French windfarms, and Olive Tree Lab-Suite v4.0 software which uses wave based geometrical acoustics to calculate sound propagation, including atmospheric refraction. The goal is to combine both approaches and introduce and test key parameters for wind turbine noise prediction. Calculation results are compared to long term noise & meteorological measurements. A good correlation is shown between calculation and measurements even in case of complex meteorological situations.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact