Similar to air reverberation chambers, non-anechoic water tanks are important acoustic measurement devices that can be used to measure the sound power radiated from complex underwater sound sources using diffusion fie...Similar to air reverberation chambers, non-anechoic water tanks are important acoustic measurement devices that can be used to measure the sound power radiated from complex underwater sound sources using diffusion field theory. However,the problem of the poor applicability of low-frequency measurements in these tanks has not yet been solved. Therefore,we propose a low-frequency acoustic measurement method based on sound-field correction(SFC) in an enclosed space that effectively solves the problem of measuring the sound power from complex sound sources below the Schroeder cutoff frequency in a non-anechoic tank. Using normal mode theory, the transfer relationship between the mean-square sound pressure in an underwater enclosed space and the free-field sound power of the sound source is established, and this is regarded as a correction term for the sound field between this enclosed space and the free field. This correction term can be obtained based on previous measurements of a known sound source. This term can then be used to correct the mean-square sound pressure excited by any sound source to be tested in this enclosed space and equivalently obtain its free-field sound power. Experiments were carried out in a non-anechoic water tank(9.0 m × 3.1 m × 1.7 m) to confirm the validity of the SFC method. Through measurements with a spherical sound source(whose free-field radiation characteristics are known),the correction term of the sound field between this water tank and the free field was obtained. On this basis, the sound power radiated from a cylindrical shell model under the action of mechanical excitation was measured. The measurement results were found to have a maximum deviation of 2.9 d B from the free-field results. These results show that the SFC method has good applicability in the frequency band above the first-order resonant frequency in a non-anechoic tank. This greatly expands the potential low-frequency applications of non-anechoic tanks.展开更多
Within previous EU projects, possible modifications to the engine components have been investigated, that would allow for an optimised aerodynamic or acoustic design of the EGV （exit guide vanes） of the TEC （turbin...Within previous EU projects, possible modifications to the engine components have been investigated, that would allow for an optimised aerodynamic or acoustic design of the EGV （exit guide vanes） of the TEC （turbine exit casing）. However, the engine weight should not be increased and the aerodynamic performance must be at least the same. This paper compares the sound power level of a state-of-the-art TEC （reference TEC） with typical EGVs with an aerodynamically optimised TEC configuration for the engine operating point approach. It is shown that a significant weight reduction （only bladings considered） and reduction in engine length can be achieved but the sound power level for the fundamental tone （lst blade passing frequency） for this acoustically important operating point is increased. It is also shown that the losses of the aerodynamical optimised EGVs are higher for this off design point but significantly lower at the aero design point. Measurements were conducted in the STTF （subsonic test turbine facility） at the Institute for Thermal Turbo machinery and Machine Dynamics, Graz University of Technology. The inlet guide vanes, the LPT （low pressure turbine） stage, and the EGVs have been designed by MTU Aero Engines.展开更多
A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power al...A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power along some simple paths on the surfaces such as rectangle, disc and hemisphere is analyzed. It is argued that the accuracy of estimating sound power is strongly depended on a suitable selection of scan path. The accurate estdriation of sound power can be made by scanning along some simple paths.展开更多
The determination of the sound power of a source is simple in a reverberation chamber , but usually lower valves are obtained at low frequencies than the free - space value . It is shown that the sound power determine...The determination of the sound power of a source is simple in a reverberation chamber , but usually lower valves are obtained at low frequencies than the free - space value . It is shown that the sound power determined in a reverberation chamber depends not only on its free - space power , but also on the positions of the source and the reveiver , as well as the way the measurements are made and averaged . Exact and statistical formulas are derived to account for these factors . The results explain the discrepancy and agree well with earlier experiments . Based on the theory ,parcticable techniques of sound power determination are proposed and correct power formulas presented .展开更多
Sound power determination of a source based on sound pressure measurements has been standardized internationally and that based on intensity measurements is in the process of standardization. The basic idea is that th...Sound power determination of a source based on sound pressure measurements has been standardized internationally and that based on intensity measurements is in the process of standardization. The basic idea is that the sound power emission of a source (machinery, equipment, etc.) is a characteristic constant of the source. A velocity monopole of strength q=Q exp(iωt) will emit a power ρf^2Q^2/2c in free space,展开更多
The Steered Response Power(SRP)method works well for sound source localization in noisy and reverberant environment.However,the large computation complexity limits its practical application.In this paper,a fast SRP se...The Steered Response Power(SRP)method works well for sound source localization in noisy and reverberant environment.However,the large computation complexity limits its practical application.In this paper,a fast SRP search method is proposed to reduce the computational complexity using small-aperture microphone array.The proposed method inspired by the SRP spatial spectrum includes two steps:first,the proposed method estimates the azimuth of the sound source roughly and determines whether the sound source is in far field or near field;then,different fine searching operations are performed according to the sound source being in far field or near field.Experiments both in simulation environments and real environments have been performed to compare the localization accuracy and computation complexity of the proposed method with those of the conventional SRP-PHAT algorithm.The results show that,the proposed method has a comparative accuracy with the conventional SRP algorithm,and achieves a reduction of 93.62%in computation complexity compared to the conventional SRP algorithm.展开更多
以双层隔振系统为研究对象,建立双层隔振系统的三维有限元模型。在给定的刚度范围内,单独改变设备隔振器刚度值或者底座隔振器刚度值时发现,任意一层隔振器刚度的变化对各级隔振均产生一定的影响。从底座隔振器与设备隔振器刚度比的角...以双层隔振系统为研究对象,建立双层隔振系统的三维有限元模型。在给定的刚度范围内,单独改变设备隔振器刚度值或者底座隔振器刚度值时发现,任意一层隔振器刚度的变化对各级隔振均产生一定的影响。从底座隔振器与设备隔振器刚度比的角度出发,对两层隔振器的刚度进行适配,研究结果表明:在刚度适配时,可能出现振动传递过程中振动放大的情况;当刚度比相同时,在刚度值较小的工况下传递到底座上的振动加速度级比刚度值较大的工况小,同时其整体隔振效果也更好;在所计算的工况中,最优刚度适配工况下的整体隔振效果比最差刚度适配工况提高9.8 dB,传递到底座的振动加速度级降低12.3 d B,辐射声功率级总值降低12.8 dB。展开更多
A numerical and experimental study was presented on active control of structurally radiated sound from an elastic cylindrical shell.An analytical model was developed for the active structural acoustic control (ASAC) o...A numerical and experimental study was presented on active control of structurally radiated sound from an elastic cylindrical shell.An analytical model was developed for the active structural acoustic control (ASAC) of the cylindrical shell.Both global and local control strategies were considered.The optimal control forces corresponding to each control strategy were obtained by using the linear quadratic optimal control theory.Numerical simulations were performed to examine and analyze the control performance under different control strategies.The results show that global sound attenuation of the cylindrical shell at resonance frequencies can be achieved by using point force as the control input of the ASAC system.Better control performance can be obtained under the control strategy of minimization of the radiated sound power.However,control spillover may occur at off-resonance frequencies with the control strategy of structural kinetic energy minimization in terms of the radiated sound power.Considerable levels of global sound attenuation can also be achieved in the on-resonance cases with the local control strategy,i.e.,minimization of the mean-square velocity of finite discrete locations.An ASAC experiment using an FXLMS algorithm was implemented,agreement was observed between the numerical and experimental results,and successful attenuation of structural vibration and radiated sound was achieved.展开更多
An analysis is made of the problem of sound radiation from infinite one-dimensional plateson elastic foundation, when the plates are subjected to the action of harmonic line forces movingat subsonic speeds (M 【 1). T...An analysis is made of the problem of sound radiation from infinite one-dimensional plateson elastic foundation, when the plates are subjected to the action of harmonic line forces movingat subsonic speeds (M 【 1). The expressions of nondimensional sound power are formulated andthe asymptotic forms of sound power in the low frequency regions are derived. The radiatedsound power is shown as a function of the stiffness of elastic foundation, in terms of stiffness fac-torψ, the moving speed of line force, in terms of Math number M, and the frequency, in termsof wavenumber ratio γ . The effects of the parameter ψ in conjunction with the parameters Mand γ on the radiated sound power level and the phenomenon of coincidence radiation are alsoinvestigated in detail.展开更多
In the natural environment,non-stationary background noise affects the animal sound recognition directly.Given this problem,a new technology of animal sound recognition based on energy-frequency(E-F)feature is propose...In the natural environment,non-stationary background noise affects the animal sound recognition directly.Given this problem,a new technology of animal sound recognition based on energy-frequency(E-F)feature is proposed in this paper.The animal sound is turned into spectrogram to show the energy,time and frequency characteristics.The sub-band frequency division and sub-band energy division are carried out on the spectrogram for extracting the statistical characteristic of energy and frequency,so as to achieve sub-band power distribution(SPD)and sub-band division.Radon transform(RT)and discrete wavelet transform(DWT)are employed to obtain the important projection coefficients,and the energy values of sub-band frequencies are calculated to extract the sub-band frequency feature.The E-F feature is formed by combining the SPD feature and sub-band energy value feature.The classification is achieved by support vector machine(SVM)classifier.The experimental results show that the method can achieve better recognition effect even when the SNR is below10 dB.展开更多
基金the National Natural Science Foundation of China (Grant No. 11874131)Open Fund Project of Key Laboratory of Underwater Acoustic Countermeasures Technology (Grant No. 2021-JCJQ-LB033-05)。
文摘Similar to air reverberation chambers, non-anechoic water tanks are important acoustic measurement devices that can be used to measure the sound power radiated from complex underwater sound sources using diffusion field theory. However,the problem of the poor applicability of low-frequency measurements in these tanks has not yet been solved. Therefore,we propose a low-frequency acoustic measurement method based on sound-field correction(SFC) in an enclosed space that effectively solves the problem of measuring the sound power from complex sound sources below the Schroeder cutoff frequency in a non-anechoic tank. Using normal mode theory, the transfer relationship between the mean-square sound pressure in an underwater enclosed space and the free-field sound power of the sound source is established, and this is regarded as a correction term for the sound field between this enclosed space and the free field. This correction term can be obtained based on previous measurements of a known sound source. This term can then be used to correct the mean-square sound pressure excited by any sound source to be tested in this enclosed space and equivalently obtain its free-field sound power. Experiments were carried out in a non-anechoic water tank(9.0 m × 3.1 m × 1.7 m) to confirm the validity of the SFC method. Through measurements with a spherical sound source(whose free-field radiation characteristics are known),the correction term of the sound field between this water tank and the free field was obtained. On this basis, the sound power radiated from a cylindrical shell model under the action of mechanical excitation was measured. The measurement results were found to have a maximum deviation of 2.9 d B from the free-field results. These results show that the SFC method has good applicability in the frequency band above the first-order resonant frequency in a non-anechoic tank. This greatly expands the potential low-frequency applications of non-anechoic tanks.
文摘Within previous EU projects, possible modifications to the engine components have been investigated, that would allow for an optimised aerodynamic or acoustic design of the EGV （exit guide vanes） of the TEC （turbine exit casing）. However, the engine weight should not be increased and the aerodynamic performance must be at least the same. This paper compares the sound power level of a state-of-the-art TEC （reference TEC） with typical EGVs with an aerodynamically optimised TEC configuration for the engine operating point approach. It is shown that a significant weight reduction （only bladings considered） and reduction in engine length can be achieved but the sound power level for the fundamental tone （lst blade passing frequency） for this acoustically important operating point is increased. It is also shown that the losses of the aerodynamical optimised EGVs are higher for this off design point but significantly lower at the aero design point. Measurements were conducted in the STTF （subsonic test turbine facility） at the Institute for Thermal Turbo machinery and Machine Dynamics, Graz University of Technology. The inlet guide vanes, the LPT （low pressure turbine） stage, and the EGVs have been designed by MTU Aero Engines.
文摘A mathematical model of deterndulng sound power by using the scanning method is developed. It is assumed that the scanning speed is constant and the noise source is stationary The accuracy of estimating sound power along some simple paths on the surfaces such as rectangle, disc and hemisphere is analyzed. It is argued that the accuracy of estimating sound power is strongly depended on a suitable selection of scan path. The accurate estdriation of sound power can be made by scanning along some simple paths.
文摘The determination of the sound power of a source is simple in a reverberation chamber , but usually lower valves are obtained at low frequencies than the free - space value . It is shown that the sound power determined in a reverberation chamber depends not only on its free - space power , but also on the positions of the source and the reveiver , as well as the way the measurements are made and averaged . Exact and statistical formulas are derived to account for these factors . The results explain the discrepancy and agree well with earlier experiments . Based on the theory ,parcticable techniques of sound power determination are proposed and correct power formulas presented .
文摘Sound power determination of a source based on sound pressure measurements has been standardized internationally and that based on intensity measurements is in the process of standardization. The basic idea is that the sound power emission of a source (machinery, equipment, etc.) is a characteristic constant of the source. A velocity monopole of strength q=Q exp(iωt) will emit a power ρf^2Q^2/2c in free space,
基金Supported by the National Natural Science Foundation of China(No.61201345)the Beijing Key Laboratory of Advanced Information Science and Network Technology(No.XDXX1308)
文摘The Steered Response Power(SRP)method works well for sound source localization in noisy and reverberant environment.However,the large computation complexity limits its practical application.In this paper,a fast SRP search method is proposed to reduce the computational complexity using small-aperture microphone array.The proposed method inspired by the SRP spatial spectrum includes two steps:first,the proposed method estimates the azimuth of the sound source roughly and determines whether the sound source is in far field or near field;then,different fine searching operations are performed according to the sound source being in far field or near field.Experiments both in simulation environments and real environments have been performed to compare the localization accuracy and computation complexity of the proposed method with those of the conventional SRP-PHAT algorithm.The results show that,the proposed method has a comparative accuracy with the conventional SRP algorithm,and achieves a reduction of 93.62%in computation complexity compared to the conventional SRP algorithm.
文摘以双层隔振系统为研究对象,建立双层隔振系统的三维有限元模型。在给定的刚度范围内,单独改变设备隔振器刚度值或者底座隔振器刚度值时发现,任意一层隔振器刚度的变化对各级隔振均产生一定的影响。从底座隔振器与设备隔振器刚度比的角度出发,对两层隔振器的刚度进行适配,研究结果表明:在刚度适配时,可能出现振动传递过程中振动放大的情况;当刚度比相同时,在刚度值较小的工况下传递到底座上的振动加速度级比刚度值较大的工况小,同时其整体隔振效果也更好;在所计算的工况中,最优刚度适配工况下的整体隔振效果比最差刚度适配工况提高9.8 dB,传递到底座的振动加速度级降低12.3 d B,辐射声功率级总值降低12.8 dB。
基金Supported by the National Natural Science Foundation of China (No.10802024)Research Fund for the Doctoral Program of Higher Education of China (No. 200802171009)+2 种基金the Natural Science Foundation of Heilongjiang Province (No.E200944)Innovative Talents Fund of Harbin (No.2009RFQXG211)Fundamental Research Fund of HEU (No. HEUFT08003)
文摘A numerical and experimental study was presented on active control of structurally radiated sound from an elastic cylindrical shell.An analytical model was developed for the active structural acoustic control (ASAC) of the cylindrical shell.Both global and local control strategies were considered.The optimal control forces corresponding to each control strategy were obtained by using the linear quadratic optimal control theory.Numerical simulations were performed to examine and analyze the control performance under different control strategies.The results show that global sound attenuation of the cylindrical shell at resonance frequencies can be achieved by using point force as the control input of the ASAC system.Better control performance can be obtained under the control strategy of minimization of the radiated sound power.However,control spillover may occur at off-resonance frequencies with the control strategy of structural kinetic energy minimization in terms of the radiated sound power.Considerable levels of global sound attenuation can also be achieved in the on-resonance cases with the local control strategy,i.e.,minimization of the mean-square velocity of finite discrete locations.An ASAC experiment using an FXLMS algorithm was implemented,agreement was observed between the numerical and experimental results,and successful attenuation of structural vibration and radiated sound was achieved.
文摘An analysis is made of the problem of sound radiation from infinite one-dimensional plateson elastic foundation, when the plates are subjected to the action of harmonic line forces movingat subsonic speeds (M 【 1). The expressions of nondimensional sound power are formulated andthe asymptotic forms of sound power in the low frequency regions are derived. The radiatedsound power is shown as a function of the stiffness of elastic foundation, in terms of stiffness fac-torψ, the moving speed of line force, in terms of Math number M, and the frequency, in termsof wavenumber ratio γ . The effects of the parameter ψ in conjunction with the parameters Mand γ on the radiated sound power level and the phenomenon of coincidence radiation are alsoinvestigated in detail.
基金Supported by the National Natural Science Foundation of China(No.61075022)
文摘In the natural environment,non-stationary background noise affects the animal sound recognition directly.Given this problem,a new technology of animal sound recognition based on energy-frequency(E-F)feature is proposed in this paper.The animal sound is turned into spectrogram to show the energy,time and frequency characteristics.The sub-band frequency division and sub-band energy division are carried out on the spectrogram for extracting the statistical characteristic of energy and frequency,so as to achieve sub-band power distribution(SPD)and sub-band division.Radon transform(RT)and discrete wavelet transform(DWT)are employed to obtain the important projection coefficients,and the energy values of sub-band frequencies are calculated to extract the sub-band frequency feature.The E-F feature is formed by combining the SPD feature and sub-band energy value feature.The classification is achieved by support vector machine(SVM)classifier.The experimental results show that the method can achieve better recognition effect even when the SNR is below10 dB.
