The Experts below are selected from a list of 6102 Experts worldwide ranked by ideXlab platform
Andries De Boer - One of the best experts on this subject based on the ideXlab platform.
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prediction of Sound absorption of stacked granular materials for normal and oblique Incident Sound waves
Acta Acustica United With Acustica, 2018Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:Tire-road noise is a problem in many (densely) populated areas. It can be significantly reduced by using porous asphalt concrete. A challenge is to develop porous asphalt concrete, such that the most dominant frequencies in tire-road noise will be absorbed by the road surface. It is especially important to also reduce and absorb oblique Incident Sound waves, since tires radiate noise normal to the tire surface, which means oblique Incident waves on the road surface. Predicting the behavior of porous asphalt concrete using models is complex, especially when non-local effects and scattering effects are included. The objective of this paper is to show a modeling approach to predict Sound absorption for oblique Incident waves in three-dimensional porous materials. Using this method, one is able to predict the Sound absorption of porous road surfaces in the design phase. This modeling approach includes a two-step approach in which first the viscothermal energy dissipation inside the pores between the rigid materials (stones) are estimated and then, secondly, the non-local effects such as scattering on the st ones within the porous road surface are computed using a finite element model. The combination of both Sound fields gives the total Sound field in and above the three-dimensional porous material, which is used to determine the Sound absorption coefficient. The analytical viscothermal and scattering solution are discussed in this paper and the modeling approach is validated with experiments using a box with stacked marbles for several angles of incidence.
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three dimensional modelling of Sound absorption in porous asphalt pavement for oblique Incident waves
10th European Congress and Exposition on Noise Control Engineering EuroNoise 2015, 2015Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:Sound absorption of porous asphalt pavements is an important property when reducing tyre-road noise. A hybrid model has been developed to predict the Sound absorption of porous roads. This model is a combination of an analytical analysis of the Sound eld and a numerical approach, including both the viscothermal e ects and the scattering e ects. The model provides a description of the three- dimensional Sound eld in and above the porous asphalt pavement and can be used to predict the absorption coe cient for oblique Incident Sound waves.
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On the Sound absorption coefficient of porous asphalt pavements for oblique Incident Sound waves
2014Co-Authors: Marieke Bezemer-krijnen, Ysbrand H. Wijnant, Andries De Boer, Dirk BekkeAbstract:A rolling tyre radiates noise in all directions. Conventional measurement techniques for the Sound absorption of road surfaces, however, only give the absorption coefficient for normal incidence. The absorption coefficient for oblique incidence is often computed assuming a locally reacting surface. In this paper, a measurement technique is described with which it is possible to perform in situ Sound absorption measurements for oblique incidence. The measurements are performed with a small 3D microphone array. The theory behind the measurement technique is based on the local plane wave assumption. In this paper, an approach is proposed to determine whether a surface behaves as a locally reacting surface or as a non-locally reacting surface, which is an important characteristic for optimising the noise absorption properties of asphalt pavements and for modelling techniques. Preliminary measurements at various angles of incidence are performed to demonstrate this approach as well as measurements of the absorption coefficient at normal incidence to validate the microphone array technique with impedance tube measurements.
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modelling absorption in porous asphalt concrete for oblique Incident Sound waves
26th International Conference on Noise and Vibration Engineering ISMA 2014, 2014Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:A numerical model to predict the Sound absorption of porous asphalt has been developed. The approach is a combination between a microstructural approach and a finite element approach. The model used to describe the viscothermal properties of the air inside the pores of the asphalt is the low reduced frequency model (LRF). The geometry of the porous asphalt is implemented directly in the FEM model, where a fast simulation will give both the viscothermal losses of the Sound energy within the pores as well as the scattering due to the stones.
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an alternative coefficient for Sound absorption
25th International Conference on Noise and Vibration Engineering ISMA 2012, 2013Co-Authors: Ysbrand H. Wijnant, E R Kuipers, Andries De BoerAbstract:The acoustic absorption coefficient is a number that indicates which fraction of the Incident acoustic power impinging on a surface is being absorbed. The Incident acoustic power is obtained by spatial integration of the Incident intensity, which is (classically) defined as the time-averaged intensity associated with the Incident Sound field. The measurement of the effective, in situ, Sound absorption coefficient is problematic as the determination thus requires a decomposition of the Sound field in an Incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the Incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the Sound field in Incident and reflected waves. Hence, one does not need to have prior information about the Incident Sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any Sound field, either transient or stationary, free field and diffuse/(semi-) reverberant Sound fields. The alternative coefficient is illustrated by means of several numerical examples.
Georg Schmitz - One of the best experts on this subject based on the ideXlab platform.
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random Incident Sound waves for fast compressed pulse echo ultraSound imaging
Internaltional Ultrasonics Symposium, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:Multiple research groups have recently innovated image recovery methods for fast pulse-echo ultraSound imaging (UI) that combine inverse scattering techniques with compressed sensing (CS). These methods alleviate the inherent tradeoff between the image quality and the image acquisition rate. The choice of the Incident Sound field is a crucial degree of freedom to implement the specific requirements of CS, e.g. incoherent measurements. Previous publications exclusively investigated steered plane waves (PWs). In this study, we leverage three types of random ultrasonic waves to better conform with the requirements of CS. This increases both the image quality and the speed of convergence.
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fast compressive pulse echo ultraSound imaging using random Incident Sound fields
Journal of the Acoustical Society of America, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying combinations of random time delays and random apodization weights. Using simulated and experimentally obtained radio frequency signals, we demonstrate that these Sound fields significantly reduce the recovery errors and improve the rate of convergence for low signal-to-noise ratios.In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying comb...
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fast compressive pulse echo ultraSound imaging using random Incident Sound fields
Journal of the Acoustical Society of America, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying combinations of random time delays and random apodization weights. Using simulated and experimentally obtained radio frequency signals, we demonstrate that these Sound fields significantly reduce the recovery errors and improve the rate of convergence for low signal-to-noise ratios.
John L Davy - One of the best experts on this subject based on the ideXlab platform.
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the directivity of Sound radiated from openings and single leaf panels exited by Incident Sound
ICSV 26, 2019Co-Authors: John L Davy, J Cambridge, J PearseAbstract:It is important for acousticians to know the directivity of the Sound radiated from openings and single panels exited by Sound Incident on their other side. Davy has published a series of papers on the theory of the directivity of the Sound radiated from openings and single leaf panels. For a single leaf panel, significantly above the coincidence frequency for a fixed angle of radiation or significantly above the coincidence angle for a fixed frequency, the previous version of Davy's theory underesti-mates the measured Sound pressure level. This underestimation has now been addressed by using the wave impedance of an infinite version of the panel with the restriction that the magnitude of the imaginary part of the wave impedance is less than or equal to that of an infinite limp version of the panel. Since the publication of Davy's papers on directivity, the authors have been able to access more experimental measurements with which to compare Davy's theory. This paper gives the results of comparisons between Davy's theory and these experimental values of directivity by giving the mean and standard deviation of the differences between the experimental and theoretical relative Sound pressure levels at an angle to the normal of the opening or single leaf panel of Sound radiation or Sound incidence. For single leaf panels, the value of the damping loss factor which was used in the theory to minimize the root mean square sum of the mean and standard deviation of the differences between theory and experiment is also given. These values of damping loss factor are much larger than normal for the materials of which the panels are constructed. The need for these large damping loss factors and the restriction on the wave impedance is believed to be due to the finite size of the panel.
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the forced radiation efficiency of finite size flat panels that are excited by Incident Sound
Journal of the Acoustical Society of America, 2009Co-Authors: John L DavyAbstract:The radiation efficiency of an infinite flat panel that radiates a plane wave into a half space is equal to the inverse of the cosine of the angle between the direction of propagation of the plane wave and the normal to the panel. The fact that this radiation efficiency tends to infinity as the angle tends to 90 degrees causes problems with simple theories of Sound insulation. Sato calculated numerical values of radiation efficiency for a finite size rectangular panel in an infinite baffle whose motion is forced by Sound Incident at an angle to the normal from the other side. This paper presents a simple two dimensional analytic strip theory, which agrees reasonably well with Sato's numerical calculations for a rectangular panel. This leads to the conclusion that it is mainly the length of the panel in the direction of radiation, rather than its width that is important in determining its radiation efficiency. A low frequency correction is added to the analytic strip theory. The theory is analytically integrated over all angles of incidence, with the appropriate weighting function, to obtain the diffuse Sound field forced radiation efficiency of a panel.
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the forced radiation efficiency of finite size flat panels that are excited by Incident Sound
Journal of the Acoustical Society of America, 2009Co-Authors: John L DavyAbstract:The radiation efficiency of an infinite flat panel that radiates a plane wave into a half space is equal to the inverse of the cosine of the angle between the direction of propagation of the plane wave and the normal to the panel. The fact that this radiation efficiency tends to infinity as the angle tends to 90° causes problems with simple theories of Sound insulation. Sato calculated numerical values of radiation efficiency for a finite size rectangular panel in an infinite baffle whose motion is forced by Sound Incident at an angle to the normal from the other side. This paper presents a simple two dimensional analytic strip theory, which agrees reasonably well with Sato’s numerical calculations for a rectangular panel. This leads to the conclusion that it is mainly the length of the panel in the direction of radiation, rather than its width that is important in determining its radiation efficiency. A low frequency correction is added to the analytic strip theory. The theory is analytically integrated over all angles of incidence, with the appropriate weighting function, to obtain the diffuse Sound field forced radiation efficiency of a panel.
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the angular distribution of Sound Incident on a panel or opening
Journal of the Acoustical Society of America, 2006Co-Authors: John L Davy, Thomas K JohnAbstract:A theoretical method has been developed for predicting the directivity of the Sound that is radiated from a panel or opening excited by Sound Incident on the other side. This directivity needs to be known when predicting the Sound level at a particular position due to Sound radiation from a roof, wall, ventilating duct, or chimney flue. The method uses a two‐dimensional strip model and the low‐frequency result for a square piston. It was found necessary to use a weighting function in order to account for the angular distribution of the Incident Sound. Initially a cosine squared weighting function with a weighting angle parameter was chosen and the weighting angle parameter was varied in order to obtain the best agreement with experiment for the particular situation. This talk will describe the theoretical development of weighting functions, which are based on the actual physics of each situation. Situations that are covered include an opening or panel on the surface of a room and an opening at the end of a duct. The method will be compared with published experimental results on the directivity of the forced Sound radiation from panels and the Sound radiation from openings.
Ysbrand H. Wijnant - One of the best experts on this subject based on the ideXlab platform.
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prediction of Sound absorption of stacked granular materials for normal and oblique Incident Sound waves
Acta Acustica United With Acustica, 2018Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:Tire-road noise is a problem in many (densely) populated areas. It can be significantly reduced by using porous asphalt concrete. A challenge is to develop porous asphalt concrete, such that the most dominant frequencies in tire-road noise will be absorbed by the road surface. It is especially important to also reduce and absorb oblique Incident Sound waves, since tires radiate noise normal to the tire surface, which means oblique Incident waves on the road surface. Predicting the behavior of porous asphalt concrete using models is complex, especially when non-local effects and scattering effects are included. The objective of this paper is to show a modeling approach to predict Sound absorption for oblique Incident waves in three-dimensional porous materials. Using this method, one is able to predict the Sound absorption of porous road surfaces in the design phase. This modeling approach includes a two-step approach in which first the viscothermal energy dissipation inside the pores between the rigid materials (stones) are estimated and then, secondly, the non-local effects such as scattering on the st ones within the porous road surface are computed using a finite element model. The combination of both Sound fields gives the total Sound field in and above the three-dimensional porous material, which is used to determine the Sound absorption coefficient. The analytical viscothermal and scattering solution are discussed in this paper and the modeling approach is validated with experiments using a box with stacked marbles for several angles of incidence.
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three dimensional modelling of Sound absorption in porous asphalt pavement for oblique Incident waves
10th European Congress and Exposition on Noise Control Engineering EuroNoise 2015, 2015Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:Sound absorption of porous asphalt pavements is an important property when reducing tyre-road noise. A hybrid model has been developed to predict the Sound absorption of porous roads. This model is a combination of an analytical analysis of the Sound eld and a numerical approach, including both the viscothermal e ects and the scattering e ects. The model provides a description of the three- dimensional Sound eld in and above the porous asphalt pavement and can be used to predict the absorption coe cient for oblique Incident Sound waves.
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On the Sound absorption coefficient of porous asphalt pavements for oblique Incident Sound waves
2014Co-Authors: Marieke Bezemer-krijnen, Ysbrand H. Wijnant, Andries De Boer, Dirk BekkeAbstract:A rolling tyre radiates noise in all directions. Conventional measurement techniques for the Sound absorption of road surfaces, however, only give the absorption coefficient for normal incidence. The absorption coefficient for oblique incidence is often computed assuming a locally reacting surface. In this paper, a measurement technique is described with which it is possible to perform in situ Sound absorption measurements for oblique incidence. The measurements are performed with a small 3D microphone array. The theory behind the measurement technique is based on the local plane wave assumption. In this paper, an approach is proposed to determine whether a surface behaves as a locally reacting surface or as a non-locally reacting surface, which is an important characteristic for optimising the noise absorption properties of asphalt pavements and for modelling techniques. Preliminary measurements at various angles of incidence are performed to demonstrate this approach as well as measurements of the absorption coefficient at normal incidence to validate the microphone array technique with impedance tube measurements.
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modelling absorption in porous asphalt concrete for oblique Incident Sound waves
26th International Conference on Noise and Vibration Engineering ISMA 2014, 2014Co-Authors: Marieke Bezemerkrijnen, Ysbrand H. Wijnant, Andries De BoerAbstract:A numerical model to predict the Sound absorption of porous asphalt has been developed. The approach is a combination between a microstructural approach and a finite element approach. The model used to describe the viscothermal properties of the air inside the pores of the asphalt is the low reduced frequency model (LRF). The geometry of the porous asphalt is implemented directly in the FEM model, where a fast simulation will give both the viscothermal losses of the Sound energy within the pores as well as the scattering due to the stones.
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an alternative coefficient for Sound absorption
25th International Conference on Noise and Vibration Engineering ISMA 2012, 2013Co-Authors: Ysbrand H. Wijnant, E R Kuipers, Andries De BoerAbstract:The acoustic absorption coefficient is a number that indicates which fraction of the Incident acoustic power impinging on a surface is being absorbed. The Incident acoustic power is obtained by spatial integration of the Incident intensity, which is (classically) defined as the time-averaged intensity associated with the Incident Sound field. The measurement of the effective, in situ, Sound absorption coefficient is problematic as the determination thus requires a decomposition of the Sound field in an Incident and reflected field which, generally, is virtually impossible to do. This paper introduces an alternative coefficient with which the effective acoustic absorption can be expressed. This coefficient is based on an alternative definition of the Incident intensity; the time average of the positive values of the instantaneous intensity. The alternative coefficient is much easier to use in a sense that it follows directly from an in situ, instantaneous intensity measurement. The coefficient does not rely on any assumptions other than the assumption that the linearized wave equation is satisfied (and thus the acoustic energy corollary). As a result, one does not need to decompose the Sound field in Incident and reflected waves. Hence, one does not need to have prior information about the Incident Sound field. Accordingly, one does not need to have prior information about the source. The coefficient can be determined in any Sound field, either transient or stationary, free field and diffuse/(semi-) reverberant Sound fields. The alternative coefficient is illustrated by means of several numerical examples.
Martin Schiffner - One of the best experts on this subject based on the ideXlab platform.
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random Incident Sound waves for fast compressed pulse echo ultraSound imaging
Internaltional Ultrasonics Symposium, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:Multiple research groups have recently innovated image recovery methods for fast pulse-echo ultraSound imaging (UI) that combine inverse scattering techniques with compressed sensing (CS). These methods alleviate the inherent tradeoff between the image quality and the image acquisition rate. The choice of the Incident Sound field is a crucial degree of freedom to implement the specific requirements of CS, e.g. incoherent measurements. Previous publications exclusively investigated steered plane waves (PWs). In this study, we leverage three types of random ultrasonic waves to better conform with the requirements of CS. This increases both the image quality and the speed of convergence.
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fast compressive pulse echo ultraSound imaging using random Incident Sound fields
Journal of the Acoustical Society of America, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying combinations of random time delays and random apodization weights. Using simulated and experimentally obtained radio frequency signals, we demonstrate that these Sound fields significantly reduce the recovery errors and improve the rate of convergence for low signal-to-noise ratios.In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying comb...
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fast compressive pulse echo ultraSound imaging using random Incident Sound fields
Journal of the Acoustical Society of America, 2017Co-Authors: Martin Schiffner, Georg SchmitzAbstract:In fast pulse-echo ultraSound imaging (UI), the image quality is traded off against the image acquisition rate by reducing the number of sequential wave emissions per image. To alleviate this tradeoff, the concept of compressed sensing (CS) was proposed by the authors in previous studies. CS regularizes the linear inverse scattering problem (ISP) associated with fast pulse-echo UI by postulating the existence of a nearly-sparse representation of the object to be imaged. This representation is obtained by a known linear transform, e.g., the Fourier or a wavelet transform. A central degree of freedom in the regularized ISP is the choice of the Incident Sound fields. Previous studies focused exclusively on steered plane waves. In this study, we investigate the usage of random Incident Sound fields to improve the relevant mathematical properties of the scattering operator governing the linear ISP. These Sound fields are synthesized by a linear transducer array whose physical elements are excited applying combinations of random time delays and random apodization weights. Using simulated and experimentally obtained radio frequency signals, we demonstrate that these Sound fields significantly reduce the recovery errors and improve the rate of convergence for low signal-to-noise ratios.
