Pub Date : 2015-02-16DOI: 10.1142/S0218396X14500155
Qunlin Zhang, Y. Mao, D. Qi, Yuanyuan Gu
Multi-frequency calculation is usually very time-consuming due to the repeated numerical integration for numerous frequencies in acoustic scattering or radiation problems. A series expansion method has been proposed to speed up this process just by taking the frequency-dependent terms out of the integral sign. However, this method, constrained by the number of truncation terms, is only applicable to low and medium frequencies and/or small-size structures. This paper develops an improved series expansion method that can be employed in a wider frequency band and larger-scale problems but with less computing expense. In the present method, the frequency-dependent term kr in the integral kernel is firstly transformed into the range from -π to π due to the periodicity of sine and cosine functions. Afterwards, truncation error would be kept reasonably small while the number of expansion terms would not increase with kr. Test cases of acoustic radiation from a pulsating sphere and a cat's eye structure are conducted and numerical results show significant reduction of computational time but suffering little accuracy loss for multi-frequency problems with this approach.
{"title":"An Improved Series Expansion Method to Accelerate the Multi-Frequency Acoustic Radiation Prediction","authors":"Qunlin Zhang, Y. Mao, D. Qi, Yuanyuan Gu","doi":"10.1142/S0218396X14500155","DOIUrl":"https://doi.org/10.1142/S0218396X14500155","url":null,"abstract":"Multi-frequency calculation is usually very time-consuming due to the repeated numerical integration for numerous frequencies in acoustic scattering or radiation problems. A series expansion method has been proposed to speed up this process just by taking the frequency-dependent terms out of the integral sign. However, this method, constrained by the number of truncation terms, is only applicable to low and medium frequencies and/or small-size structures. This paper develops an improved series expansion method that can be employed in a wider frequency band and larger-scale problems but with less computing expense. In the present method, the frequency-dependent term kr in the integral kernel is firstly transformed into the range from -π to π due to the periodicity of sine and cosine functions. Afterwards, truncation error would be kept reasonably small while the number of expansion terms would not increase with kr. Test cases of acoustic radiation from a pulsating sphere and a cat's eye structure are conducted and numerical results show significant reduction of computational time but suffering little accuracy loss for multi-frequency problems with this approach.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"44 1","pages":"1450015"},"PeriodicalIF":0.0,"publicationDate":"2015-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X14500155","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-02-16DOI: 10.1142/S0218396X14500131
Izhak Levi, Eli Turkel, D. Givoli
Time reversal is a powerful procedure in application fields involving wave propagation. It is based on the invariance of the wave equations, in the absence of dissipation, in the time direction. This allows going backward in time to recover past events. We use time reversal to recover the location of a source applied at the initial time based on measurements at a later time. We generalize the procedure previously developed for the scalar wave equation1 to elastodynamics. We show that the technique is quite robust, sometimes even in the presence of very high noise levels. Also it is not very sensitive to the medium characterizations, when a sufficient amount of measurement data is available. We extend previous work to get good refocusing for multiple sources. We introduce a new score to assess the quality of the numerical solution for the refocusing problem which produces good results. Furthermore, we use the refocusing technique as a basis for scatterer location recovery. By adding noise in a controlled manner we improve the scheme of finding the location of the scatterer.
{"title":"Time Reversal for Elastic Wave Refocusing and Scatterer Location Recovery","authors":"Izhak Levi, Eli Turkel, D. Givoli","doi":"10.1142/S0218396X14500131","DOIUrl":"https://doi.org/10.1142/S0218396X14500131","url":null,"abstract":"Time reversal is a powerful procedure in application fields involving wave propagation. It is based on the invariance of the wave equations, in the absence of dissipation, in the time direction. This allows going backward in time to recover past events. We use time reversal to recover the location of a source applied at the initial time based on measurements at a later time. We generalize the procedure previously developed for the scalar wave equation1 to elastodynamics. We show that the technique is quite robust, sometimes even in the presence of very high noise levels. Also it is not very sensitive to the medium characterizations, when a sufficient amount of measurement data is available. We extend previous work to get good refocusing for multiple sources. We introduce a new score to assess the quality of the numerical solution for the refocusing problem which produces good results. Furthermore, we use the refocusing technique as a basis for scatterer location recovery. By adding noise in a controlled manner we improve the scheme of finding the location of the scatterer.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"23 1","pages":"1450013"},"PeriodicalIF":0.0,"publicationDate":"2015-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X14500131","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-02-16DOI: 10.1142/S0218396X15500010
Jun Xu, Xiaodong Li, Yueping Guo
Acoustic liners are widely used in commercial aero-engine to suppress noise. In theoretical investigations, the liner geometry is often assumed as an array of symmetric micro resonator with orifice or slit at the center. However, in real application, orifices or slits distributed in micro resonator are offset. For better understanding of sound absorption mechanism of micro resonator with offset slits under high incident sound pressure level (SPL), direct numerical simulations (DNS) using high order low dispersion and low dissipation computational aeroacoustics (CAA) method are carried out. The simulations are first validated by experimental data, showing good agreement and establishing the relevance of the simulation methodology. Numerical simulations of resonators with single offset slit or two slits are then conducted. The two sound absorption mechanisms, namely viscous dissipation and vortex shedding, are discussed with detailed numerical data and analysis, which lead to quantitative parametric description of the energy partition between the two mechanisms as a function of both frequency and geometry. It is shown that offset slit can reduce vortex shedding and results in less sound absorption. The effects of more than one slit are, however, opposite; more vortex shedding occurs with more slits so that sound absorption is enhanced. This may potentially help guide liner design in practical applications.
{"title":"A Numerical Investigation on Sound Absorption Mechanism of Micro Resonator with Offset Slits","authors":"Jun Xu, Xiaodong Li, Yueping Guo","doi":"10.1142/S0218396X15500010","DOIUrl":"https://doi.org/10.1142/S0218396X15500010","url":null,"abstract":"Acoustic liners are widely used in commercial aero-engine to suppress noise. In theoretical investigations, the liner geometry is often assumed as an array of symmetric micro resonator with orifice or slit at the center. However, in real application, orifices or slits distributed in micro resonator are offset. For better understanding of sound absorption mechanism of micro resonator with offset slits under high incident sound pressure level (SPL), direct numerical simulations (DNS) using high order low dispersion and low dissipation computational aeroacoustics (CAA) method are carried out. The simulations are first validated by experimental data, showing good agreement and establishing the relevance of the simulation methodology. Numerical simulations of resonators with single offset slit or two slits are then conducted. The two sound absorption mechanisms, namely viscous dissipation and vortex shedding, are discussed with detailed numerical data and analysis, which lead to quantitative parametric description of the energy partition between the two mechanisms as a function of both frequency and geometry. It is shown that offset slit can reduce vortex shedding and results in less sound absorption. The effects of more than one slit are, however, opposite; more vortex shedding occurs with more slits so that sound absorption is enhanced. This may potentially help guide liner design in practical applications.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"23 1","pages":"1550001"},"PeriodicalIF":0.0,"publicationDate":"2015-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X15500010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64076128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-02-16DOI: 10.1142/S0218396X15500034
Y. Qi, S. Zhou, Renhe Zhang, Yun Ren
A formula for the instantaneous phase of the cross-correlation function of two different modes using the relationship between the horizontal wavenumber difference and frequency described by the waveguide invariant is deduced in this paper. Based on the formula, a waveguide-invariant-based warping operator suitable for both reflected and refracted modes in shallow water at low frequency is presented, providing an effective tool to filter the cross-correlation function of modes from the signal autocorrelation function. Using the phase of the filtered cross-correlation component in the frequency domain, a passive source ranging method on a single hydrophone is proposed. Simulated and experimental data using impulsive signals verify the validity of the derived warping operator and source ranging method.
{"title":"A Waveguide-Invariant-Based Warping Operator and Its Application to Passive Source Range Estimation","authors":"Y. Qi, S. Zhou, Renhe Zhang, Yun Ren","doi":"10.1142/S0218396X15500034","DOIUrl":"https://doi.org/10.1142/S0218396X15500034","url":null,"abstract":"A formula for the instantaneous phase of the cross-correlation function of two different modes using the relationship between the horizontal wavenumber difference and frequency described by the waveguide invariant is deduced in this paper. Based on the formula, a waveguide-invariant-based warping operator suitable for both reflected and refracted modes in shallow water at low frequency is presented, providing an effective tool to filter the cross-correlation function of modes from the signal autocorrelation function. Using the phase of the filtered cross-correlation component in the frequency domain, a passive source ranging method on a single hydrophone is proposed. Simulated and experimental data using impulsive signals verify the validity of the derived warping operator and source ranging method.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"23 1","pages":"1550003"},"PeriodicalIF":0.0,"publicationDate":"2015-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X15500034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64076329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-02-16DOI: 10.1142/S0218396X15500022
G. Yoon
This research aims to develop a novel unified analysis method for an acoustic-porous-structure multiphysics interaction system when the porous medium is modeled by the empirical Delany–Bazley formulation. Multiphysics analysis of acoustic structure interaction is commonly performed by solving the linear elasticity and Helmholtz equations separately and enforcing a mutual coupling boundary condition. If the pressure attenuation from a porous material is additionally considered, the multiphysics analysis becomes highly intricate, because three different media (acoustic, porous, and elastic structures) with different governing equations and interaction boundary conditions should be properly formulated. To overcome this difficulty, this paper proposes the application of a novel mixed formulation to consider the mutual coupling effects among the acoustic, fibrous (porous), and elastic structure media. By combining the mixed finite element formulation with the Delany–Bazley formulation, a multiphysics simulation of sound propagation considering the coupling effects among the three media can be easily conducted. To show the validity of the present unified approach, several benchmark problems are considered.
{"title":"Unified Analysis with Mixed Finite Element Formulation for Acoustic-Porous-Structure Multiphysics System","authors":"G. Yoon","doi":"10.1142/S0218396X15500022","DOIUrl":"https://doi.org/10.1142/S0218396X15500022","url":null,"abstract":"This research aims to develop a novel unified analysis method for an acoustic-porous-structure multiphysics interaction system when the porous medium is modeled by the empirical Delany–Bazley formulation. Multiphysics analysis of acoustic structure interaction is commonly performed by solving the linear elasticity and Helmholtz equations separately and enforcing a mutual coupling boundary condition. If the pressure attenuation from a porous material is additionally considered, the multiphysics analysis becomes highly intricate, because three different media (acoustic, porous, and elastic structures) with different governing equations and interaction boundary conditions should be properly formulated. To overcome this difficulty, this paper proposes the application of a novel mixed formulation to consider the mutual coupling effects among the acoustic, fibrous (porous), and elastic structure media. By combining the mixed finite element formulation with the Delany–Bazley formulation, a multiphysics simulation of sound propagation considering the coupling effects among the three media can be easily conducted. To show the validity of the present unified approach, several benchmark problems are considered.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"23 1","pages":"1550002"},"PeriodicalIF":0.0,"publicationDate":"2015-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X15500022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64076215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-18DOI: 10.1142/S0218396X14500118
Gang Ye, Chunhua Deng, Q. Liu
The thermoacoustic tomography (TAT) is a novel noninvasive and nonionizing medical imaging modality for breast cancer detection. In the TAT, a short pulse of microwave is irradiated to the breast tissue. The tissue absorbs the microwave energy and is heated up momentarily, thus it generates acoustic waves due to the thermoelastic expansion. If the pulse width of the microwave radiation is around one microsecond, the generated acoustic waves are ultrasonic and are in the MHz range. Wide-band ultrasonic transducers are employed to acquire the time-resolved ultrasound signals, which carry information about the microwave absorption properties (mainly related to conductivities) of different tissues. An image showing such properties can then be reconstructed from the time-resolved ultrasound signals. Most existing TAT reconstruction methods are based on the assumption that the tissue under study is acoustically homogeneous. In practice, however, most biological tissues are inhomogeneous. For example, the speed of sound has about 10% variation in breast tissue. The acoustic heterogeneity will cause phase distortion of the pressure field, which will in turn cause blurring in the reconstructed image, thus limiting the ability to resolve small objects. In this work, a 3D inhomogeneous reconstruction method based on pseudo-spectral time-domain (PSTD) is presented to overcome this problem. The method includes two steps. The first step is a homogeneous reconstruction process, from which an initial image is obtained. Since the inhomogeneity itself is usually an acoustic source, the shape and location of the inhomogeneity can be estimated. Then, the acoustic properties of the inhomogeneities (available from the literatures for known tissue types) are assigned to the classified regions, and the other reconstruction based on the updated acoustic property map is conducted. With this process, the phase distortion can be effectively corrected. So it can improve the ability to image small objects. A 3D breast phantom is used to study the proposed method. The breast phantom was generated based on the data set of the Visible Human Project. Regions of different tissue types have been classified and acoustic and electric properties are assigned to such regions. Small phantom tumors placed in the breast phantom have been reconstructed successfully with the inhomogeneous reconstruction method. Improved resolution has been achieved compared to that obtained by homogeneous method.
{"title":"The PSTD Method with the 4th-Order Time Integration for 3D TAT Reconstruction of a Breast Model","authors":"Gang Ye, Chunhua Deng, Q. Liu","doi":"10.1142/S0218396X14500118","DOIUrl":"https://doi.org/10.1142/S0218396X14500118","url":null,"abstract":"The thermoacoustic tomography (TAT) is a novel noninvasive and nonionizing medical imaging modality for breast cancer detection. In the TAT, a short pulse of microwave is irradiated to the breast tissue. The tissue absorbs the microwave energy and is heated up momentarily, thus it generates acoustic waves due to the thermoelastic expansion. If the pulse width of the microwave radiation is around one microsecond, the generated acoustic waves are ultrasonic and are in the MHz range. Wide-band ultrasonic transducers are employed to acquire the time-resolved ultrasound signals, which carry information about the microwave absorption properties (mainly related to conductivities) of different tissues. An image showing such properties can then be reconstructed from the time-resolved ultrasound signals. Most existing TAT reconstruction methods are based on the assumption that the tissue under study is acoustically homogeneous. In practice, however, most biological tissues are inhomogeneous. For example, the speed of sound has about 10% variation in breast tissue. The acoustic heterogeneity will cause phase distortion of the pressure field, which will in turn cause blurring in the reconstructed image, thus limiting the ability to resolve small objects. In this work, a 3D inhomogeneous reconstruction method based on pseudo-spectral time-domain (PSTD) is presented to overcome this problem. The method includes two steps. The first step is a homogeneous reconstruction process, from which an initial image is obtained. Since the inhomogeneity itself is usually an acoustic source, the shape and location of the inhomogeneity can be estimated. Then, the acoustic properties of the inhomogeneities (available from the literatures for known tissue types) are assigned to the classified regions, and the other reconstruction based on the updated acoustic property map is conducted. With this process, the phase distortion can be effectively corrected. So it can improve the ability to image small objects. A 3D breast phantom is used to study the proposed method. The breast phantom was generated based on the data set of the Visible Human Project. Regions of different tissue types have been classified and acoustic and electric properties are assigned to such regions. Small phantom tumors placed in the breast phantom have been reconstructed successfully with the inhomogeneous reconstruction method. Improved resolution has been achieved compared to that obtained by homogeneous method.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"22 1","pages":"1450011"},"PeriodicalIF":0.0,"publicationDate":"2014-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X14500118","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-18DOI: 10.1142/S0218396X14500143
Yong Chen, Yiyong Huang, Xiaoqian Chen, Dengpeng Hu
This paper deals with the axisymmetric acoustic wave propagating along the perfect gas in the presence of a uniform flow confined by a rigid-walled pipeline. Under the linear acoustic assumption, mathematical formulation of wave propagation is deduced from the conservations of mass, momentum and energy. Meanwhile a method based on the Fourier–Bessel theory is introduced to solve the problem. Comprehensive comparisons of the phase velocity and wave attenuation between the non-isentropic and isentropic acoustic waves are provided. Meanwhile the effects of flow profile, acoustic frequency, and pipeline radius are analyzed.
{"title":"Axisymmetric Wave Propagation in Uniform Gas Flow Confined by Rigid-Walled Pipeline","authors":"Yong Chen, Yiyong Huang, Xiaoqian Chen, Dengpeng Hu","doi":"10.1142/S0218396X14500143","DOIUrl":"https://doi.org/10.1142/S0218396X14500143","url":null,"abstract":"This paper deals with the axisymmetric acoustic wave propagating along the perfect gas in the presence of a uniform flow confined by a rigid-walled pipeline. Under the linear acoustic assumption, mathematical formulation of wave propagation is deduced from the conservations of mass, momentum and energy. Meanwhile a method based on the Fourier–Bessel theory is introduced to solve the problem. Comprehensive comparisons of the phase velocity and wave attenuation between the non-isentropic and isentropic acoustic waves are provided. Meanwhile the effects of flow profile, acoustic frequency, and pipeline radius are analyzed.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"22 1","pages":"1450014"},"PeriodicalIF":0.0,"publicationDate":"2014-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X14500143","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-18DOI: 10.1142/S0218396X14500106
X. Xiao, R. Chen
The propagation of elastic longitudinal waves in one-dimensional (1D) phononic crystals (PNCs) consisting of alternating solid and fluid media is comprehensively analyzed in theory. We demonstrate the acoustic band gap (ABG) structure determined by the dispersion relation for longitudinal waves at normal incidence. According to the band structure, we design a sub-PNC by setting a reasonable thickness ratio of fluid and solid media, and then form a phononic heterostructure by merging this PNC and other PNC designed in advance. We have shown that the wide band gap exists in such a phononic heterostructure for elastic longitudinal waves at normal incidence. For oblique incidence, the wide band gap shifts towards high frequency regions, meanwhile a low-frequency band gap is split.
{"title":"Acoustic Band Gap Extension in One-Dimensional Solid/Fluid Phononic Crystal Heterostructure","authors":"X. Xiao, R. Chen","doi":"10.1142/S0218396X14500106","DOIUrl":"https://doi.org/10.1142/S0218396X14500106","url":null,"abstract":"The propagation of elastic longitudinal waves in one-dimensional (1D) phononic crystals (PNCs) consisting of alternating solid and fluid media is comprehensively analyzed in theory. We demonstrate the acoustic band gap (ABG) structure determined by the dispersion relation for longitudinal waves at normal incidence. According to the band structure, we design a sub-PNC by setting a reasonable thickness ratio of fluid and solid media, and then form a phononic heterostructure by merging this PNC and other PNC designed in advance. We have shown that the wide band gap exists in such a phononic heterostructure for elastic longitudinal waves at normal incidence. For oblique incidence, the wide band gap shifts towards high frequency regions, meanwhile a low-frequency band gap is split.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"22 1","pages":"1450010"},"PeriodicalIF":0.0,"publicationDate":"2014-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X14500106","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075332","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-18DOI: 10.1142/S0218396X1450012X
Yi Wei Lin, G. Too
Acoustic contrast control is a sound focusing technique applied to personal audio system devices to provide the optimal sound contrast for increasing or decreasing the potential sound energy of a specific area. In this study, acoustic contrast control was developed for sound focusing in shallow water. The advantage of this technique is the establishment of two zones: a bright zone around the user and a dark zone for other regions. In the acoustic contrast control process, computational ocean acoustics are used to calculate the Green's function between the source point and the field point. The effects of environmental parameters, which comprised the number of control sources, transmission frequency, control distances between sources and control zone of a geometric location were simulated. The results show that acoustic contrast control is an effective approach for sound focusing in shallow water that can increase the potential sound energy of a specific area. Employing this technique can also enhance underwater communications by using frequency-shift keying modulation for cross-talking applications.
{"title":"A Parametric Study of Sound Focusing in Shallow Water by Using Acoustic Contrast Control","authors":"Yi Wei Lin, G. Too","doi":"10.1142/S0218396X1450012X","DOIUrl":"https://doi.org/10.1142/S0218396X1450012X","url":null,"abstract":"Acoustic contrast control is a sound focusing technique applied to personal audio system devices to provide the optimal sound contrast for increasing or decreasing the potential sound energy of a specific area. In this study, acoustic contrast control was developed for sound focusing in shallow water. The advantage of this technique is the establishment of two zones: a bright zone around the user and a dark zone for other regions. In the acoustic contrast control process, computational ocean acoustics are used to calculate the Green's function between the source point and the field point. The effects of environmental parameters, which comprised the number of control sources, transmission frequency, control distances between sources and control zone of a geometric location were simulated. The results show that acoustic contrast control is an effective approach for sound focusing in shallow water that can increase the potential sound energy of a specific area. Employing this technique can also enhance underwater communications by using frequency-shift keying modulation for cross-talking applications.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"22 1","pages":"1450012"},"PeriodicalIF":0.0,"publicationDate":"2014-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X1450012X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64075495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-18DOI: 10.1142/S0218396X1450009X
G. Jourdain, L. Eriksson
A time domain perforated plate model based on the "homogenization" concept is presented; the dynamic porous wall model. This model takes into account linear and nonlinear losses as well as inertial effects due to the unsteady flow in the vicinity of the holes. A numerical validation of the dynamic porous wall model is performed via the computation of the impedance versus frequency for an acoustic liner consisting of a solid wall back sheet and a perforated face sheet, separated by a given distance. Two types of unsteady flow are considered; firstly 3D LES in which the holes in the perforated face sheet are fully resolved, and secondly 2D URANS simulations in which the dynamic porous wall model is used to include the effects of the perforated face sheet. Comparisons of the results show that the new dynamic porous wall model captures both nonlinear and inertial effects well.
{"title":"Numerical Validation of a Time Domain Perforated Plate Model with Nonlinear and Inertial Effects","authors":"G. Jourdain, L. Eriksson","doi":"10.1142/S0218396X1450009X","DOIUrl":"https://doi.org/10.1142/S0218396X1450009X","url":null,"abstract":"A time domain perforated plate model based on the \"homogenization\" concept is presented; the dynamic porous wall model. This model takes into account linear and nonlinear losses as well as inertial effects due to the unsteady flow in the vicinity of the holes. A numerical validation of the dynamic porous wall model is performed via the computation of the impedance versus frequency for an acoustic liner consisting of a solid wall back sheet and a perforated face sheet, separated by a given distance. Two types of unsteady flow are considered; firstly 3D LES in which the holes in the perforated face sheet are fully resolved, and secondly 2D URANS simulations in which the dynamic porous wall model is used to include the effects of the perforated face sheet. Comparisons of the results show that the new dynamic porous wall model captures both nonlinear and inertial effects well.","PeriodicalId":54860,"journal":{"name":"Journal of Computational Acoustics","volume":"22 1","pages":"1450009"},"PeriodicalIF":0.0,"publicationDate":"2014-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1142/S0218396X1450009X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64074632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：