Two optimal beamforming approaches for sensor arrays with arbitrary shapes and element directivities are proposed. The first one minimizes the sidelobe level while keeping the distortionless response in the direction ...Two optimal beamforming approaches for sensor arrays with arbitrary shapes and element directivities are proposed. The first one minimizes the sidelobe level while keeping the distortionless response in the direction of the desired signal and maintaining the mainlobe width. The second approach maximizes the array gain while keeping the mainlobe direction and controling the sidelobe level which is strictly guaranteed to be below a prescribed value. Array weight norm constraint is used to improve the robustness of the two optimal beamforming approaches against random errors. The first approach provides the optimal tradeoff among the sidelobe level, the beamwidth and robustness; and the second approach provides the optimal tradeoff among the array gain, the sidelobe level and robustness. Both optimal beamforming problems are formulated as the second-order cone programming which can be easily solved using well-developed interior-point methods. Results of computer simulations and lake-experiment for a circular array demonstrate superior performance of the approaches proposed in this paper in comparison to some existing adaptive-based algorithms.展开更多
An approach to designing time domain broadband frequency invariant beamformer via optimal array pattern synthesis and optimal FIR filters design is proposed. First, the working frequency band is decomposed into a numb...An approach to designing time domain broadband frequency invariant beamformer via optimal array pattern synthesis and optimal FIR filters design is proposed. First, the working frequency band is decomposed into a number of narrow band frequency bins.The array weights at each frequency bin are designed via optimal array pattern synthesis methods to insure that the synthesized pattern approximates the desired one within the mainlobe area. Then, a bank of FIR filters corresponding to the input channels are designed to provide the frequency responses that approximate the array weights in the working frequency band for each sensor. Finally, each sensor feeds a FIR filter and the filter outputs are summed to produce the beam output time series. Both array pattern synthesis and FIR filters design problems are formulated as the second-order cone programming (SOCP), which can be easily solved using well-developed interior-point methods. Results of computer simulations and lake-experiment for a twelve-element semicircular array demonstrate satisfactory performance of the proposed approach.展开更多
Based on nearfield sound pressure sensing to pick up error information, an approach for constructing active acoustic structure to effectively reduce radiated sound power at low frequency is proposed. The idea is that ...Based on nearfield sound pressure sensing to pick up error information, an approach for constructing active acoustic structure to effectively reduce radiated sound power at low frequency is proposed. The idea is that a nearfield pressure after active control is used as error signals and transformed into an objective function in adaptive active control process. Firstly sound power expression using near-field pressure radiated from a flexible structure is derived, and then three kind of nearfield pressure based active control strategies, i.e. minimization of radiated sound power, minimization of sound power for dominant radiation modes and minimization of sound power for modified dominant radiation modes are respectively presented and applied to active control of radiated single and broadband noise. Finally computer simulations on sound power reduction under three strategies are conducted and it is shown that the proposed active control strategies are invalid and considerable reduction in radiated sound power can be achieved.展开更多
Based on adaptive technique, a design method for broadband array with frequency invariant beam pattern is presented. For a given beam pattern, the all design process can be completed automatically by computer without ...Based on adaptive technique, a design method for broadband array with frequency invariant beam pattern is presented. For a given beam pattern, the all design process can be completed automatically by computer without deriving expression of weight vector. The design process is divided into three steps: (1) Evaluate the weight vector in reference frequency by numerical method. (2) Obtain the weight vectors in other frequency by adaptive technique. (3) For the design target of frequency response given by weight vector at different frequency point, design FIR filter. The proposed method can be applied to arbitrary array and have no restriction on element patterns.展开更多
Time-frequency analysis is combined with array processing to develop a direction of arrival (DOA) estimation method. The array data model is constructed in time-frequency domain by cross time-frequency distribution be...Time-frequency analysis is combined with array processing to develop a direction of arrival (DOA) estimation method. The array data model is constructed in time-frequency domain by cross time-frequency distribution between the output of a reference sensor and those of two symmetric sub-arrays. Accordingly a subspace method is presented based on the average of two sub-arrays' time-frequency data vector model instead of the conventional array model, to estimate DOAs of multiple signals. Because the array data is processed both in spatial domain and 2-D time-frequency domain, the proposed method has an ability to select the signal of interesting, and is suitable for non-stationary signal. Additionally, the method is robust to noise and holds an advantage of low computational load. Simulations are conducted to verify the efficiency of the method and comparision is made with other methods.展开更多
To quickly obtain the sound speed profile (SSP) in shallow water by inversion methods, an inversion scheme for SSP in shallow water using matched-beam processing (MBI) is developed. The cost function of MBI is based o...To quickly obtain the sound speed profile (SSP) in shallow water by inversion methods, an inversion scheme for SSP in shallow water using matched-beam processing (MBI) is developed. The cost function of MBI is based on matched-beam concept. It is verified experimentally that MBI is feasible and superior in comparison to conventional matched-field inversion (MFI) by using the East China Sea Experiment data. The SSP inverted by MBI using the wide-band explosion signals is in good agreement with the results measured based on conductivity, temperature and depth (CTD) in the experiment. And the root of mean square error of the inverted SSP is less than 2 m/s. Research results have shown that MBI is robust with respect to the sediment parameters mismatch. And SSP in shallow water can be more quickly obtained by MBI than by MFI.展开更多
A Bayesian high-resolution direction-of-arrival (DOA) estimator is proposed based on the maximum a posteriori principle. The statistical performance of the Bayesian high-resolution DOA estimator is also investigated. ...A Bayesian high-resolution direction-of-arrival (DOA) estimator is proposed based on the maximum a posteriori principle. The statistical performance of the Bayesian high-resolution DOA estimator is also investigated. Comparison with MUSIC and Maximum likelihood estimator (MLE) shows that the Bayesian method has higher resolution and more accurate estimates for either incoherent or coherent sources. It is also more robust in the case of low SNR.展开更多
Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to A...Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed. Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.展开更多
The performance of the multistage Constant Modulus (CM) array, one of the most striking blind beamforming algorithms, for the source Directions-of-Arrival (DOA) estimation was analyzed via computer simulations and wat...The performance of the multistage Constant Modulus (CM) array, one of the most striking blind beamforming algorithms, for the source Directions-of-Arrival (DOA) estimation was analyzed via computer simulations and water tank experiments, and was compared to that of other DOA estimation algorithms including the 'non-blind' and the 'blind'. Firstly, a nominal array model and an array model with gain and phase perturbations were established, respectively. Secondly, the multistage CM array algorithm was described and computer simulations were conducted. Simulation results showed that the multistage CM array could correctly estimate the DOA at the same time when the sources were blindly recovered, and the angle separating ability of the algorithm was beyond the Rayleigh resolution limit. By changing the variance of the array model errors, it was also verified that the multistage CM array was more robust to the errors than some other algorithms mentioned in this paper. Finally, water tank experiments and data processing results were provided. Situations with different array sizes and source angular separations were considered. It was shown that the results were in good agreement with computer simulations. Results of computer simulations and water tank experiments verified that the DOAs of the multiple independent sources could be blindly and robustly estimated with the multistage CM array.展开更多
After analyzed Fourth Order Cumulant (FOC) of harmonic signals theoretically, the FOC is divided into three parts. The first is the cubic frequency (phase) coupling components. The second is the double frequency (phas...After analyzed Fourth Order Cumulant (FOC) of harmonic signals theoretically, the FOC is divided into three parts. The first is the cubic frequency (phase) coupling components. The second is the double frequency (phase) coupling components (w1+w2=w3+w4). The last is the rest components. On the basis of the study, the FOC diagonal slice is used to extract the cubic frequency (phase) coupling feature, double frequency (phase) coupling feature and the 'sub-band energy' feature of ship-radiated noise. In terms of the features, the three type ships are classified by artificial neural network. The correct classification rates of A, B and C ships are 92.5%, 92.7%, 88.6%, respectively. The results show the method is effective and practical.展开更多
The evaluation of creep damages of Cr-Mo-V steel used in the gas turbine of power plant has been carried out using the line-focus-beam (LFB) acoustic microscopy. The velocity of leaky surface acoustic wave (LSAW) prop...The evaluation of creep damages of Cr-Mo-V steel used in the gas turbine of power plant has been carried out using the line-focus-beam (LFB) acoustic microscopy. The velocity of leaky surface acoustic wave (LSAW) propagated near the specimen surface was used for the quantitative evaluations, which was measured by LFB acoustic microscopy using the v(z) curve analysis method. It has been shown that with the increase of creep damage fraction of metal material the LSAW velocity decreases obviously, which suggests the possibility of nondestructive and quantitative evaluations of creep damages in metal materials by acoustic microscopy.展开更多
A method of two-dimensional direction of arrival (DOA) estimation for low altitude target, which is based on intensity measurement using a three-dimensional differential pressure acoustic vector-sensor, is presented. ...A method of two-dimensional direction of arrival (DOA) estimation for low altitude target, which is based on intensity measurement using a three-dimensional differential pressure acoustic vector-sensor, is presented. With the perfect characteristics of acoustic vector sensor in the low frequency band, accurate DOA estimation is achieved under small array size. The validity of the proposed method was assessed by experiments on the noise signals radiated by a helicopter. The influence of acoustic sensor size, integral time and signal to noise ratio to the accuracy of DOA estimation were investigated, respectively. The performance comparisons demonstrated that it outperformed the traditional time-delay measurement based method for a small acoustic array.展开更多
文摘Two optimal beamforming approaches for sensor arrays with arbitrary shapes and element directivities are proposed. The first one minimizes the sidelobe level while keeping the distortionless response in the direction of the desired signal and maintaining the mainlobe width. The second approach maximizes the array gain while keeping the mainlobe direction and controling the sidelobe level which is strictly guaranteed to be below a prescribed value. Array weight norm constraint is used to improve the robustness of the two optimal beamforming approaches against random errors. The first approach provides the optimal tradeoff among the sidelobe level, the beamwidth and robustness; and the second approach provides the optimal tradeoff among the array gain, the sidelobe level and robustness. Both optimal beamforming problems are formulated as the second-order cone programming which can be easily solved using well-developed interior-point methods. Results of computer simulations and lake-experiment for a circular array demonstrate superior performance of the approaches proposed in this paper in comparison to some existing adaptive-based algorithms.
基金This work was supported by the National Natural Science Foundation of China (60472073) and (10304015).
文摘An approach to designing time domain broadband frequency invariant beamformer via optimal array pattern synthesis and optimal FIR filters design is proposed. First, the working frequency band is decomposed into a number of narrow band frequency bins.The array weights at each frequency bin are designed via optimal array pattern synthesis methods to insure that the synthesized pattern approximates the desired one within the mainlobe area. Then, a bank of FIR filters corresponding to the input channels are designed to provide the frequency responses that approximate the array weights in the working frequency band for each sensor. Finally, each sensor feeds a FIR filter and the filter outputs are summed to produce the beam output time series. Both array pattern synthesis and FIR filters design problems are formulated as the second-order cone programming (SOCP), which can be easily solved using well-developed interior-point methods. Results of computer simulations and lake-experiment for a twelve-element semicircular array demonstrate satisfactory performance of the proposed approach.
基金the National Natural Science Foundation of China(10274060)and the Aeronautic Science Foundation of China(01I50307).
文摘Based on nearfield sound pressure sensing to pick up error information, an approach for constructing active acoustic structure to effectively reduce radiated sound power at low frequency is proposed. The idea is that a nearfield pressure after active control is used as error signals and transformed into an objective function in adaptive active control process. Firstly sound power expression using near-field pressure radiated from a flexible structure is derived, and then three kind of nearfield pressure based active control strategies, i.e. minimization of radiated sound power, minimization of sound power for dominant radiation modes and minimization of sound power for modified dominant radiation modes are respectively presented and applied to active control of radiated single and broadband noise. Finally computer simulations on sound power reduction under three strategies are conducted and it is shown that the proposed active control strategies are invalid and considerable reduction in radiated sound power can be achieved.
基金This work was supported by the National Natural Science Foundation of China (60272077)
文摘Based on adaptive technique, a design method for broadband array with frequency invariant beam pattern is presented. For a given beam pattern, the all design process can be completed automatically by computer without deriving expression of weight vector. The design process is divided into three steps: (1) Evaluate the weight vector in reference frequency by numerical method. (2) Obtain the weight vectors in other frequency by adaptive technique. (3) For the design target of frequency response given by weight vector at different frequency point, design FIR filter. The proposed method can be applied to arbitrary array and have no restriction on element patterns.
文摘Time-frequency analysis is combined with array processing to develop a direction of arrival (DOA) estimation method. The array data model is constructed in time-frequency domain by cross time-frequency distribution between the output of a reference sensor and those of two symmetric sub-arrays. Accordingly a subspace method is presented based on the average of two sub-arrays' time-frequency data vector model instead of the conventional array model, to estimate DOAs of multiple signals. Because the array data is processed both in spatial domain and 2-D time-frequency domain, the proposed method has an ability to select the signal of interesting, and is suitable for non-stationary signal. Additionally, the method is robust to noise and holds an advantage of low computational load. Simulations are conducted to verify the efficiency of the method and comparision is made with other methods.
文摘To quickly obtain the sound speed profile (SSP) in shallow water by inversion methods, an inversion scheme for SSP in shallow water using matched-beam processing (MBI) is developed. The cost function of MBI is based on matched-beam concept. It is verified experimentally that MBI is feasible and superior in comparison to conventional matched-field inversion (MFI) by using the East China Sea Experiment data. The SSP inverted by MBI using the wide-band explosion signals is in good agreement with the results measured based on conductivity, temperature and depth (CTD) in the experiment. And the root of mean square error of the inverted SSP is less than 2 m/s. Research results have shown that MBI is robust with respect to the sediment parameters mismatch. And SSP in shallow water can be more quickly obtained by MBI than by MFI.
基金This work was supported by the National Natural Science Foundation of China (60272076) and Doctoral Discipline Foundation.
文摘A Bayesian high-resolution direction-of-arrival (DOA) estimator is proposed based on the maximum a posteriori principle. The statistical performance of the Bayesian high-resolution DOA estimator is also investigated. Comparison with MUSIC and Maximum likelihood estimator (MLE) shows that the Bayesian method has higher resolution and more accurate estimates for either incoherent or coherent sources. It is also more robust in the case of low SNR.
基金National Natural Science Foundation of China(Grant 19904008)the Excellent Young Teachers Program of MOE,Chinathe Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China.
文摘Characteristics of radiation impedance and its inducing variation of electrical impedance for a controllable source have been investigated. An impedance-based error criterion has been proposed and its application to Active Noise Control is demonstrated through a coil driven loudspeaker. A general formula of radiation impedance is derived for two control strategies, according to the criterion of total acoustic power output. The radiation impedances of some commonly used sound sources are calculated. We discuss in detail the relation between variation of the input electrical impedance and radiation impedance for the two control strategies. The measured data of the input electrical impedance from a loudspeaker agree fairly well with theoretical analysis. An AC- bridge circuit is designed in order to measure the weak variation of electrical impedance resulted from radiation impedance. The bridge relative output is unique for a certain control strategy, from which an impedance-based error criterion is then proposed and the implementation of its application to an active control system is analyzed. Numerical results of such criterion are presented. An analogue control system is set up and experiments are carried out in a semi-anechoic chamber to verify the new control approach.
基金the Doctorate Creation Foundation of Northwestern Polytechnical University (200203).
文摘The performance of the multistage Constant Modulus (CM) array, one of the most striking blind beamforming algorithms, for the source Directions-of-Arrival (DOA) estimation was analyzed via computer simulations and water tank experiments, and was compared to that of other DOA estimation algorithms including the 'non-blind' and the 'blind'. Firstly, a nominal array model and an array model with gain and phase perturbations were established, respectively. Secondly, the multistage CM array algorithm was described and computer simulations were conducted. Simulation results showed that the multistage CM array could correctly estimate the DOA at the same time when the sources were blindly recovered, and the angle separating ability of the algorithm was beyond the Rayleigh resolution limit. By changing the variance of the array model errors, it was also verified that the multistage CM array was more robust to the errors than some other algorithms mentioned in this paper. Finally, water tank experiments and data processing results were provided. Situations with different array sizes and source angular separations were considered. It was shown that the results were in good agreement with computer simulations. Results of computer simulations and water tank experiments verified that the DOAs of the multiple independent sources could be blindly and robustly estimated with the multistage CM array.
文摘After analyzed Fourth Order Cumulant (FOC) of harmonic signals theoretically, the FOC is divided into three parts. The first is the cubic frequency (phase) coupling components. The second is the double frequency (phase) coupling components (w1+w2=w3+w4). The last is the rest components. On the basis of the study, the FOC diagonal slice is used to extract the cubic frequency (phase) coupling feature, double frequency (phase) coupling feature and the 'sub-band energy' feature of ship-radiated noise. In terms of the features, the three type ships are classified by artificial neural network. The correct classification rates of A, B and C ships are 92.5%, 92.7%, 88.6%, respectively. The results show the method is effective and practical.
文摘The evaluation of creep damages of Cr-Mo-V steel used in the gas turbine of power plant has been carried out using the line-focus-beam (LFB) acoustic microscopy. The velocity of leaky surface acoustic wave (LSAW) propagated near the specimen surface was used for the quantitative evaluations, which was measured by LFB acoustic microscopy using the v(z) curve analysis method. It has been shown that with the increase of creep damage fraction of metal material the LSAW velocity decreases obviously, which suggests the possibility of nondestructive and quantitative evaluations of creep damages in metal materials by acoustic microscopy.
基金the National Natural Science Foundation of China(60372086)and the Doctorate Foundation of Northwestern Polytechnical University,China(200204).
文摘A method of two-dimensional direction of arrival (DOA) estimation for low altitude target, which is based on intensity measurement using a three-dimensional differential pressure acoustic vector-sensor, is presented. With the perfect characteristics of acoustic vector sensor in the low frequency band, accurate DOA estimation is achieved under small array size. The validity of the proposed method was assessed by experiments on the noise signals radiated by a helicopter. The influence of acoustic sensor size, integral time and signal to noise ratio to the accuracy of DOA estimation were investigated, respectively. The performance comparisons demonstrated that it outperformed the traditional time-delay measurement based method for a small acoustic array.
