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18 August 2011, Volume 31 Issue 4 Previous Issue    Next Issue
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1.综述
2.振动理论与数值解法
3.运载工具振动与噪声
4.环境振动与环境声学
6.信号处理与故障诊断
7.减振降噪设备和器材
9.振动噪声测试技术


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1.综述

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Status Quo of Study on Machine,s Load Identification Technique HU Yin-yin;SHUAI Zhi-jun;LI Wan-you;IU Zhi-gang 2011, 31(4): 1-5.  DOI: 10.3969/j.issn.1006-1355-2011.04.001 Abstract ( )   The research method of the technique of structural dynamic load identification and its engineering applications are summarized in this paper. The status quo of the research of dynamic load identification method in the frequency-domain and time-domain, and its advantages and disadvantages are reviewed. Future development of this technique is expected. It is pointed out that improving the accuracy, simplifying the testing and numerical simulation processes, and combining with the practical models in engineering may become the main concentrations in the research area of the structural dynamic load identification. Related Articles | Metrics

2.振动理论与数值解法

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Performance of an Elastic Polymer Foam Cushion in Attenuating Responses of Shipboard Standing-men to Vertical Ship Shock WU Jing-bo;CHEN Yong;LI Zhao-jun; HUANG Jian-song;HUA Hong-xing 2011, 31(4): 6-10.  DOI: 10.3969/j.issn.1006-1355-2011.04.002 Abstract ( )   Protection of shipboard personnel from shock events induced by underwater explosion is very interesting to ship designers. In this study, the potential attenuation performance of an elastic polymer foam cushion inserted between standing-man and ship deck is investigated theoretically. An 8-DOF nonlinear lumped-parameter model is used to predict the standing-man’s biodynamic responses and injury potential. The cushion is modeled by a chain of masses separated by nonlinear springs and dampers in parallel to simulate the micro inertia, stiffness and rate-dependent effects exhibited by common polymer cellular materials. Two variables, kickoff speed (KS) ratio and deck reaction force (DRF) ratio corresponding to two types of typical injury potential of standing-men, are defined as evaluation parameters. The influence of critical buckling force level, material rate dependent effect as well as other design factors on the attenuation performance of the foam cushion is discussed in detail. Some general design rules are also presented. Related Articles | Metrics

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Research of Optimal Control Used in Double-layer Vibration Isolation System ZENG Qiang-hong;ZHU Shi-jian;YAN Zhen-tao 2011, 31(4): 11-15.  DOI: 10.3969/j.issn.1006-1355-2011.04.003 Abstract ( )   Considering force transmissibility and the magnitude of actuator output, an optimal control is applied to a double-layer vibration isolation system. The relationship between the weighting matrix and the feedback matrix is acquired. The transfer function of output performance versus input disturbance is obtained. By analyzing the amplitude and frequency characteristics of the transfer function, the affect of the weighting matrices Q and R on the system characteristics is found. Thus, the weighting function can be reasonably selected. The optimal design of the controller can be realized with the consideration of various performance objectives. Related Articles | Metrics

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Research of Method Based on Variable Friction Damping WANG Rui;HUA Hong-xing 2011, 31(4): 16-20.  DOI: 10.3969/j.issn.1006-1355-2011.04.004 Abstract ( )   Stating with passive vibration isolator adjusting the damping adaptively, a method based on variable friction damping has been developed to satisfy the vibration isolation requirement in the broadband frequency range. By considering the effect of the relative velocity between the friction contact surfaces with normal pressure, a non-linear friction model which can describe the friction force in this method has been proposed. Through the experimental design and investigation, the fitting capability of this model has been examined by parameter identification. Related Articles | Metrics

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Numerical Research on Stochastic Resonance Effect in Bistable System XIA Jun-zhong;LIU Yuan-hong;MEI Jian-min;LEN Yong-gang;ZHANG Wei-feng 2011, 31(4): 21-25.  DOI: 10.3969/j.issn.1006-1355-2011.04.005 Abstract ( )   The model of stochastic resonance in bistable system is analyzed based on adiabatic approximate theory. Ingredients of stochastic resonance, including system parameters, noise intensity, signal amplitude and frequency, are studied. It is concluded that there is an optimal noise intensity for the stochastic resonance system, and augmentation of the signal amplitude is favorable to the occurrence of stochastic resonance. However, the increase of signal frequency will cause the peak of signal in output power spectrum to leave the low-frequency area that noise energy concentrates on. It makes the peak of signal decrease rapidly and the stochastic resonance phenomena disappear gradually. For the fact that signal amplitude, frequency, noise intensity often exceed the requirements of small parameters in the adiabatic approximation theory and turn into large parameters, the re-scaling method for realization of stochastic resonance of large parameter signals is discussed. Related Articles | Metrics

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Factors Analysis of Influencing of Steel Catenary Riser WANG Hong-xia;LI Zhe 2011, 31(4): 26-28.  DOI: 10.3969/j.issn.1006-1355-2011.04.006 Abstract ( )   Generally, there is high-pressure oil or gas inside the ocean riser. The velocity of the fluid will greatly influence the vibration response of the riser. In this paper, the affect of fluid velocity in the riser on the natural frequency of steel catenary riser (SCR) structure is studied. The results show that the natural frequency decreases with the increase of fluid flow velocity. Thus, one should pay sufficient attention to this phenomenon in the design. Furthermore, the tensile variation of the SCR with the depth is calculated and analyzed. Considering the variation of the tension, the natural frequencies of the SCR is calculated. The influence of bending stiffness of the SCR on the natural frequency of the riser is analyzed. The results show that bending stiffness has little effect on the first 10-order frequencies. Therefore, it can be ignored in calculating the low-frequency mode vortex-induced vibration. Related Articles | Metrics

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Parametric Optimization of Towed Line Array ,s Vibration Isolation Modules Base on Pseudo - parallel Improved Genetic Algorithm JIANG Guo-he;XUE Feng;XU Ying-bo 2011, 31(4): 29-32.  DOI: 10.3969/j.issn.1006-1355-2011.04.007 Abstract ( )   In order to predict the vibration isolation capability of towed line array vibration isolation modules, a planar fluid-structure coupling model of the array is constructed by means of ANSYS code. And the vibration isolation capability is calculated with the consideration of the influence of the load (acoustic module) on the vibration isolation modules. Pseudo-parallel improved genetic algorithm and ANSYS’s parameterized design language APDL are combined to realize the optimization of the main parameters of the vibration isolation modules. And the optimal values of internal oil density, optimal elastic moduli of hull and the components of the isolation modules for 20Hz and 40 Hz exciting frequencies are obtained. This work provides a reference for improving the performance of vibration isolation modules. Related Articles | Metrics

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Dynamical Analysis and Simulation of Vibration System of Ultrasonic Gear Honing LI Qing-fen;LV Ming;WANG Shi-ying 2011, 31(4): 33-36.  DOI: 10.3969/j.issn.1006-1355-2011.04.007 Abstract ( )   The non-resonant design method of vibration system of ultrasonic gear honing is studied. The dynamic frequency equation of the vibration system is solved by means of MATLAB code. The effect of the design length of the horn and the vibration frequency of the amplitude transformer on the error of the solution of the frequency equation is analyzed. A set of parameters for amplitude transformer design is obtained. The resonant frequency of the transformer is derived through the modal analysis by means of ANSYS, which is consistent with the results of theoretical design. It is concluded that this non-resonant design method is feasible. Related Articles | Metrics

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Study on Effect of Ruzicka Isolator on Shock Isolation LOU Jing-jun;ZHU Shi-jian;TANG Si-mi 2011, 31(4): 37-41.  DOI: 10.3969/j.issn.1006-1355-2011.04.009 Abstract ( )   Usually, the stiffness of the conventional isolator is small because the performance of vibration isolation is preferential to that of shock isolation. This leads to high efficiency of shock isolation but large relative displacement. Moreover, the stiffness break is induced by the displacement restrictor, and the efficiency of shock isolation is deteriorated. Based on the law of conservation of energy, the conventional shock isolator and the Ruzicka isolator is modeled and analyzed, and the cushioning coefficients are obtained. Comparison shows that the Ruzicka isolator has more excellent performance than that of the conventional isolator. The shock isolation system with the Ruzicka isolator is changed to the dimensionless form with an acceleration pulse input of half sine shape. The shock response is calculated, and the parameters with high efficiency of shock isolation are obtained. The shock response shows that the maximal acceleration and relative displacement are restricted below the limit value by the Ruzicka isolator when the conventional design fails to protect the object. Related Articles | Metrics

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Experimental Study on Dynamic Character of Ring-wedge Connection Structure LIU Qing-lin;HU Shao-quan;XU You-gang 2011, 31(4): 42-45.  DOI: 10.3969/j.issn.1006-1355-2011.04.009 Abstract ( )   In the dynamic environment, there exist several nonlinear factors in the ring-wedge connection structure, such as contact, clearance and abrasion. It is hard to depict the structure’s dynamic character precisely by theoretical means. In this paper, the method of experimental modal analysis is used to identify the modal parameters of the structure. The result shows that the modal parameters of the structure change regularly with the exciting force. Then the responses of different portions of the structure excited by different magnitudes and different types of forces are studied experimentally. The result shows that the relation between the response and the excitation is nonlinear. And the nonlinearities at different measurement points are dissimilar. Related Articles | Metrics

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Modal Radiation Efficiency of the Axisymmetric Flexural Vibration Circular Plate REN Hui-juan;SHENG Mei-ping 2011, 31(4): 51-54.  DOI: 10.3969/j.issn.1006-1355-2011.04.012 Abstract ( )   The modal radiation efficiency of axisymmetric flexural vibration of circular plates with clamped, simply supported or free boundary condition is discussed by integrating the sound intensity over the surface of the plates. The numerical results are obtained by employing 10 nodes Gauss-Legender integration method. The modal radiation efficiencies with the same mode order but different boundary conditions of the plates are compared. The results show that (1) the modal radiation efficiency increases with the increasing of the frequency in the whole frequency range; (2) the modal radiation efficiency of the plate in low frequency range approaches zero, and the frequency range corresponding to the nearly-zero radiation efficiency becomes wider with the increasing of the mode order; (3) when the sound wave number of the medium is much greater than the flexural wave number of the plate, the radiation efficiency of various modes of the plate with various boundary conditions approaches 1; (4) for edge-clamped plate and simply supported plate, the radiation efficiency of the first order mode is much greater than those of the other modes, while the case is just the reverse for the free-edged plate; and (5) for modes with the same order, the radiation efficiency of the plate with clamped-edge is maximal, that of the simply supported plate takes the second place, and that of the free-edged plate is the minimum. Related Articles | Metrics

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Time-varying Weighted Combination Forecast Based on Polynomial Approximation and Its Application DENG Wei-qiang;WANG Yue-gang;YANG Ying-tao 2011, 31(4): 55-59.  DOI: 10.3969/j.issn.1006-1355-2011.04.013 Abstract ( )   The time-varying weighted combination forecast based on polynomial approximation formulas of unary and binary functions is proposed and used to model and forecast the structural response time-series of some aircrafts. Taking the unbiasedness and nonnegativity constraints into consideration, the relaxation variables are introduced to transform the inequality constraint to equality constraint, and the new objective function of the combination forecast is constructed based on penalty function. The Gene Algorithm is used to acquire the numerical solution of all variables and the function of time-varying weights. The application results verify the efficiency of this method. Related Articles | Metrics

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Prediction and Validation of Aircraft Cabin Noise by Hybrid FE-SEA Method at Mid-frequency Range LI Bing;CHEN Ke-an;PAN Kai;HU Ying 2011, 31(4): 60-63.  DOI: 10.3969/j.issn.1006-1355-2011.04.014 Abstract ( )   Prediction and experimental verification of aircraft cabin noise modeled by the hybrid FE-SEA method is carried out. The method of subsystem dividing of the cabin is introduced. The cabin’s noise spectrums in mid-frequency range under 4 different excitation conditions are simulated and thereafter compared with measurement results. It is shown that the hybrid FE-SEA method based approach is more accurate than the conventional Statistical Energy Analysis (SEA) method in predicting mid-frequency noise inside the aircraft cabin. Related Articles | Metrics

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Experimental Research on Performance of Water-lubricated Rubber Stern Bearing Based on Vibration Analysis JIN Yong;LIU Zheng-lin 2011, 31(4): 64-67.  DOI: 10.3969/j.issn.1006-1355-2011.04.015 Abstract ( )   In order to reduce vibration and noise of the marine’s stern bearing, the influence of the hardness of the rubber material on vibration of the stern shafting is studied experimentally. The vibration data of the stern bearing is gathered and analyzed through the Pulse vibration analysis platform. Through the analysis of the vibration spectrogram, it is suggested that the hardness of the inner surface of the water-lubricated rubber stern bearing, which usually operates under the conditions of low speed and heavy duty, should reach such a level as 80, and it could be slightly higher for the stern bearing which operates at medium and high speed. Related Articles | Metrics

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Transverse Vibration Analysis of Shafting Based on an Improved Fourier Series Method ZHOU Hai-jun;LV Bing-lin;DU Jing-tao;Wen L. Li;LI Wan-you 2011, 31(4): 68-72.  DOI: 10.3969/j.issn.1006-1355-2011.04.016 Abstract ( )   In this paper, an improved Fourier series method (IFSM) is employed to determine the transverse free vibration of a multi-span non-uniform shafting system with arbitrary boundary conditions. At first, the differential equation for the transverse free vibration of a uniform beam with lumped masses is formulated. Then, the mass and stiffness matrices for the shafting are derived using the IFSM, and then all the eigenvalues and eigenvectors are readily obtained by solving a standard matrix eigenvalue equation. In this method, the displacement function is expanded as a single Fourier cosine series plus an auxiliary polynomial function. The auxiliary function is used to overcome the discontinuities of the resilient boundary. Numerical results are presented to validate the correct of the method. And the stiffness effect of connecting flange is described. Related Articles | Metrics

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Physical Parameter Identification of the 6-DOF Micro-vibration Isolation Platform HOU Jun-fang;LI Rong-li;WEI Huo-ming 2011, 31(4): 73-76.  DOI: 10.3969/j.issn.1006-1355-2011.04.017 Abstract ( )   A method for physical parameter identification of the 6-DOF isolation platform based on single point DOF excitation is proposed. In this method, the coupling relation among the 6 DOFs, which comes from the simplification of the air-spring supports due to their mechanical character, is considered. The parameter of the vertical location of gravity center of the platform is used for measuring the transfer function of the isolation system. This method includes the group-measurement of the frequency response function, the identification of the vertical location parameter of the platform’s gravity center by iteration, and the respective identification of the physical parameters of sub-systems. With this method, the problem of physical parameter identification of the platform with unknown vertical location of gravity center is solved. The basis for selection of the excitation DOF of each subsystem is analyzed. Finally, the physical parameters of the isolation platform are verified by experiment. Related Articles | Metrics

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Dynamic Characteristics of an Automatic Ball Balancer under the Second Harmonic Exciting Forces TAN Qing;XIE Yan-qin;;LIU Wen-qian 2011, 31(4): 77-79.  DOI: 10.3969/j.issn.1006-1355-2011.04.018 Abstract ( )   High-speed rotating machinery is one kind of widely used mechanical equipments. Fault elimination is an important issue for the machinery. Rotor’s automatic balancing is one of the ways for solving the problem. During the operation of the machinery，in addition to eccentric excitation force, there will be high frequency and score frequency exciting forces, especially the second harmonic exciting force, acting on the rotor. Study on the influence of these exciting forces on the automatic ball balancer is of important significance. In this paper, the balance equation of the automatic ball balancer under the second harmonic exciting forces is constructed, its dynamic characteristic is analyzed using the MATLAB software and validated by the experiment. Related Articles | Metrics

3.运载工具振动与噪声

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Finite Elements Analysis of High - speed Train Wind Noise in Lighthill’s Acoustic Analogy YANG Xiao-Yu;Ya-jun CHENG;Feng-hua LIU 2011, 31(4): 80-84.  DOI: 10.3969/j.issn.1006-1355-2011.04.019 Abstract ( )   With the constant increase of the trains’ speed, the aerodynamic noise gradually succeeds the traditional track noise and becomes the main noise source of the high-speed trains. In this paper, a hybrid CFD/CAA wind noise model for the high speed trains based on Lighthill’s analogy is constructed utilizing a professional finite elements acoustic simulator ACTRAN-Aeroacoustics. Numerical results of fluid and acoustic fields are reported and discussed. Some important issues for further development of the simulation model are discussed. The simulation results show that there are three dominant locations for the aerodynamic noise sources which depend on the shape of the train. With the use of this model, the influence of the train’s shape on the wind noise can be analyzed, and the optimization for low noise design of the train can be realized. Related Articles | Metrics

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Measurement and Correlation Analysis of Ground-borne Vibration and Noise Induced by Underground Railway CHU Yi-Ping 2011, 31(4): 85-88.  DOI: 10.3969/j.issn.1006-1355-2011.04.020 Abstract ( )   The ground-borne vibration and noise induced by underground railway of 22 sensitive residential points was measured, where there is much complaint about the vibration and noise, so as to analyze the influence and correlation of underground railway’s ground-borne vibration and noise. According to the measured results and subsequent analysis, 1) the maximum ground-borne vibration level (VLZmax) of above measuring points is about 55dB~92dB, the frequency is concentrated between 40Hz~120Hz; 2) the maximum ground-borne noise level (LAmax) varies among different metro lines, and the increment is bigger within the range from 25Hz to 300Hz; 3) the attenuation of the ground-borne vibration and noise is fast within the bounds of 15 meters; 4) although the ground-borne noise is induced by the vibration, the correlation between vibration and noise is not so good, and the correlation coefficient changes with the difference of building structure, etc. Related Articles | Metrics

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Abnormal Noise Source Identification and Control of Motorcycle under Idle Condition CHU Zhi-gang;YANG Yang;JIANG Zhong-han 2011, 31(4): 89-92.  DOI: 10.3969/j.issn.1006-1355-2011.04.021 Abstract ( )   Utilizing sound intensity method, source separation method and selective sound intensity method comprehensively, the abnormal noise source of motorcycle under idle condition was identified. The production mechanism and transmission of the abnormal noise was analyzed. The results show that the frequency ranges from 891Hz to 2239Hz and the radiation noise of exhaust muffler heat shield is the dominate source and the impact to the muffler internal partitions by exhaust airflow is the root reason. The abnormal noise can be eliminated effectively by strengthening the connection stiffness of the muffler internal partitions. Related Articles | Metrics

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Interior Noise Analysis and Control of an SRV GONG Bing;CHEN Jian 2011, 31(4): 93-96.  DOI: 10.3969/j.issn.1006-1355-2011.04.022 Abstract ( )   A structural FE model for body-in-white of an SRV, an acoustic cavity BE model and an FE-BE coupled model are built. Based on the analysis of the acoustic pressure response at the field points, the peak values of acoustic pressure are found by panel contribution analysis. Based on modes modification method, the acoustic pressure is found and reduced by optimizing the velocity of the nodal point in main vibrant area. Related Articles | Metrics

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Review of Theories and Methods of Noise Source Identification of Vehicle XIONG Jian-qiang;;HUANG Ju-hua;LIAO Qun 2011, 31(4): 97-101.  DOI: 10.3969/j.issn.1006-1355-2011.04.023 Abstract ( )   The theories and methods of noise source identification of vehicles and their characteristics are summarized in this paper. It provides a reference for adopting appropriate methods for noise source identification of vehicles. It is pointed out that visualization technique is one of the most important trends for development of noise source identification. Related Articles | Metrics

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Analysis of Improvement of a Bus for Suppresing Its Abnormal Vibration and Noise YIN Ke;SONG Xiang-rong 2011, 31(4): 102-105.  DOI: 10.3969/j.issn.1006-1355-2011.04.024 Abstract ( )   A sample bus abnormally vibrates with noise when it runs at 90 km/h. It seriously deteriorates the vehicle’s NVH performance. In this paper, the time tracking of vibration frequency is done under the condition of the 5-th speed acceleration to find out the possible excitation source. The three-dimensional spectrum diagram shows that the main vibration scenarios and noise frequencies inside the bus are similar to those of the 1st and 2nd order rotation frequencies of the transmission shaft. Then, the structure of the transmission shaft is improved by strengthening the support of the shaft, adding rubber isolators and improving the suspension frame. As a result, the vibration and noise level of the entire vehicle is significantly reduced. The analysis and the test method shown in this paper provide a reference for vibration and noise reduction of vehicles. Related Articles | Metrics

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Identification of Excavator Cab’s Noise Source Based on Partial Coherence Analysis ZHANG Rong-bin; BI Chuan-xing; ZHANG Yong-bin 2011, 31(4): 106-110.  DOI: 10.3969/j.issn.1006-1355-2011.04.025 Abstract ( )   Since hydraulic excavator consists of many controlling and operating components, it has lots of noise sources, and the major noise sources are relevant. So, it is appropriate to identify the noise source of the hydraulic excavator using the partial coherence analysis. In this paper, a multi-input and single-output noise source identification model is firstly established, and then an algorithm is developed for the calculation of the partial coherence function based on Matlab. Finally, an experiment is carried out with an actual hydraulic excavator. In the experiment the main sources influencing the noise at the driver’s right-ear are identified using the partial coherence analysis. This work provides some guidance for further study of vibration and noise reduction of the excavator. Related Articles | Metrics

4.环境振动与环境声学

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Study on Urban Noise Mapping System and its Application XIA Dan 2011, 31(4): 111-114.  DOI: 10.3969/j.issn.1006-1355-2011.04.026 Abstract ( )   The necessity of establishment of noise mapping system and its functionality are described. A noise mapping system framework is established in this paper, and some pilot applications are done. Focus on the composition, the establishment procedures and the key technology of noise mapping, it will can be applied to manage urban noise, to control traffic noise and forecast sound environmental quality. Related Articles | Metrics

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Discussion of Noise Monitoring Methods of Airport Environmental-protection Acceptance Check Shen Xu-Hui 2011, 31(4): 115-119.  DOI: 10.3969/j.issn.1006-1355-2011.04.027 Abstract ( )   The airport construction in our country will develop rapidly in the period of the 12th Five-Year- Plan. By 2020, the number of airports for China’s civil aviation transportation will reach 244. The environment- protection acceptance check for airport completion has become an essential work for monitoring stations in many provinces and municipalities. Airport’s noise monitoring has been a hard work for the stations for a long time. Currently, there are very few technical specifications of noise monitoring for airport’s acceptance check. In this paper, noise monitoring methods of airport’s environment-protection acceptance check are discussed. Some examples of airport’s acceptance monitoring are provided. Related Articles | Metrics

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Enclosure Noise Source Evaluation Based on Beamforming and Transfer Path Analysis CHENG Jian;SUN Jie;LIU Bin;HUANG Zhen-yu 2011, 31(4): 119-124.  DOI: 10.3969/j.issn.1006-1355-2011.04.028 Abstract ( )   Noise source evaluation for enclosure noise control is a difficult problem due to the large amount of noise sources involved in the complicated acoustic field. In this paper, an enclosure noise source evaluation method is presented. This method mainly includes four steps: (1) dividing the enclosure space into several sub-spaces according to the potential source positions; (2) applying the beamforming method in terms of the measured A-weighting sound pressure level in each sub-space to find the significant sources;(3) computing the contribution of each significant source to the target position by the transfer path analysis (TPA), and (4) employing an error analysis of the calculated noise to verify the noise evaluation. The simulation results show that this approach can reduce the reverberation influence and TPA work. Therefore, it is a good approach for the evaluation of the enclosure noise sources Related Articles | Metrics

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Testing Study on the Sound Barrier Equivalent Frequency of Freight Trains GONG Kai;LIU Lin-ya 2011, 31(4): 124-127.  DOI: 10.3969/j.issn.1006-1355-2011.04.029 Abstract ( )   The sound barrier design has become a major theme concerned by international academic circles. Setting sound barriers on both sides of railroad track is an effective and economic method for railway’s noise control. The diffraction attenuation calculation is the kernel content of the sound barrier design, and the equivalent frequency of the sound barrier is one of the important parameters for the diffraction attenuation calculation. In order to raise the efficiency of sound barrier design, the noise frequency characteristics of freight trains in different locomotive traction and at different operating speed are studied by testing. Meanwhile, the sound barrier equivalent frequencies of freight trains under different working conditions are obtained by statistical analysis of the measured field data. Related Articles | Metrics

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Analysis of Ecological Barrier’s Reduction of the Highway’s Traffic Noise Zhang Wei-Chen 2011, 31(4): 128-131.  DOI: 10.3969/j.issn.1006-1355-2011.04.030 Abstract ( )   The classic thin barrier is appropriate for the crowded city roads but not better for the suburb open-highway. Because the houses along the highway are diversified, and the government demanded to setup 10~20m areas along the road to build up some greenbelts, it is important for highway’s noise production by increasing the barrier thickness and making the suitable form combine barrier with greenbelts. On the base of the single-double diffraction for noise barrier theory in the GBT17247.2-1998 ‘Acoustics-attenuation of sound during propagation outdoors - Part 2 : General method of calculation’, and the ecological gradient-green’s real-time test, the ecological barrier has been developed at the aims of highway’s traffic noise reduction. The optimal-combination of the barrier’s height-width has been developed by the Cadna/A Software. The design of the ecological noise barrier is contributed not only to improve the sound quality of the environment of the area’s along the highway, but also to make the landscape around the highway more beauty. When the land value along the highway is increased, the benefits between the environment and the economy will be balanced better. Related Articles | Metrics

6.信号处理与故障诊断

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Statistical Analysis for Database Dependence in Classification of Emotional Speech by using Different Features Extraction Approaches SUN Ying;ZHANG Xue-ying 2011, 31(4): 132-136.  DOI: 10.3969/j.issn.1006-1355-2011.04.031 Abstract ( )   Four approaches of feature extraction: the Linear Predictive Cepstral Coefficient (LPCC), the Teager Energy Operator (TEO), the Mel-Frequency Cepstral Coefficient (MFCC) and the Zero Crossings with Peak Amplitudes (ZCPA) are described in this paper. And these approaches are applied to emotional speech recognition. Two kinds of experiments are carried out. The first one is a kind of single language experiments with TYUT database and Berlin database. Its results show that these four approaches can represent speech emotion effectively by using single language of single database. MFCC has the best result of the four approaches. The second kind experiment is merge-database of single language. Most previous work on emotional feature extraction is based on a special language of single speech database. But in practice, the environment of the speaker is various. So the study of emotional feature extraction based on merge-database is significative. Experiments of the second kind indicate that the four features are all database dependent. ZCPA features are of the least database dependence of the four approaches. Related Articles | Metrics

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Multi-load Fault Diagnosis of Vibration Signal Based on Improved Genetic Neural Network WANG Xin;YU Hong-liang;ZHANG Lin;DUAN Shu-lin;HUANG Chao-ming 2011, 31(4): 137-141.  DOI: 10.3969/j.issn.1006-1355-2011.04.032 Abstract ( )   According to the motion law of diesel engine valve, the characteristic vector of cylinder-cover’s vibration signal is extracted by wavelet packet decomposition. For multi-load fault diagnosis, the hidden layer node number, weights and threshold of the back propagation genetic algorithms are optimized by binary and real value hybrid coding. Experiment results show that the method has obvious advantages on multi-load vibration signal fault diagnosis. It is able to improve the network learning ability, convergence speed and accuracy of detection. Related Articles | Metrics

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Application of Partial Coherence for Noise Source Identification in Aeroacoustic Wind Tunnel GU Guang-wu;ZHU Bo 2011, 31(4): 142-144.  DOI: 10.3969/j.issn.1006-1355-2011.04.033 Abstract ( )   Identification of noise source is of important significance for noise control. In this paper, a multiple input/single output model for system noise identification is established. The technique of measurement of noise source contribution and partial coherence analysis are introduced and discussed. The formula of partial coherence function is given by “residual spectrum”. Aiming at 0.55m×0.4m aeroacoustic wind tunnel, the measurement scheme is presented. According to the noise measurement data, the main noise source in aeroacoustic wind tunnel is identified. Related Articles | Metrics

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Research on Algorithm of Sound Source Identification Based on Cross-spectral Beamforming with Exclusion of Autospectra YANG Yang;CHU Zhi-gang;NI Ji-min;WANG Wei-dong 2011, 31(4): 145-148.  DOI: 10.3969/j.issn.1006-1355-2011.04.034 Abstract ( )   The principle of cross-spectral beamforming with exclusion of autospectra is analyzed based on spherical wave assumption. The result shows that the interference from the self-noise in each microphone channel is suppressed and the accuracy of sound source identification is improved by excluding the auto-spectral elements from the cross-spectral matrix. Furthermore, the algorithm of sound source identification is designed and the corresponding sound source imaging software is developed. The sources in the source plane are identified accurately. Additionally, the correctness of the designed algorithm and practical applicability of the developed software are tested and verified by an example. Based on this, the noise sound source identification test of an engine on a bench is made under the rated speed condition. The result shows that the noise at the engine head is mainly from the radiation noise of the air compressor exhaust outlet and the engine body at the upper left of the crankshaft pulley, and the noises of the left side and the right side of the engine are both mainly from the radiation noise of the engine block and the oil pan. Related Articles | Metrics

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Analysis of Over-vibration Problem of a Turbogenerator Set with a Planetary Gearbox GONG Cun-zhong 2011, 31(4): 149-151.  DOI: 10.3969/j.issn.1006-1355-2011.04.035 Abstract ( )   Under the condition of rated load and rated speed operation of a generator set, over-vibration phenomena appeared in the planetary gearbox’s bearing and the rear bearing of the generator. Through the vibration spectrum analysis, the assembling mismatch of the three planetary gears in the gearbox was found to be the main reason of the over-vibration phenomena. After dismounting, inspecting and reassembling, the assembling accuracies between the planetary gears and the internal gear rings were improved. The verification test showed that the over-vibration phenomena disappeared. Related Articles | Metrics

7.减振降噪设备和器材

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Advance in the Research of Polyurethane Vibration Isolator DING Zhen-lin 2011, 31(4): 152-154.  DOI: 10.3969/j.issn.1006-1355-2011.04.0036 Abstract ( )   Polyurethane is an elastomer with excellent synthesis performance, which has widely used in civilian engineer. The newest development of the polyurethane vibration isolator was systematically introduced, and the performance of polyurethane vibration isolator was also compared with that of the rubber isolator. The results show that the polyurethane vibration isolator defeats the rubber isolator at fatigue life, creep, carrying capacity, carrying region and isolation performance, etc. Related Articles | Metrics

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Study on Coupling Design of Engine Muffler YANG Run-chao;YAN Fu-wu;LIU Zhi-en; 2011, 31(4): 155-159.  DOI: 10.3969/j.issn.1006-1355-2011.04.037 Abstract ( )   The exhaust muffler of a minibus is designed on the basis of analyzing the exhaust spectrum of B 12 engine. An engine-muffler coupled model is built using GT - Power software. Computational simulation and experimental verification of acoustic and aerodynamic performance of the muffler are presented. The result shows that the insert loss of the muffler can reach 25dB，the tail noise is about 95dB, and the backpressure is in 34±2 kPa of the allowable range. Hence, the goal of design of the muffler is successfully reached. It is shown by mutual comparison between the simulation and test results that GT-Power software has a good performance for prediction of the acoustic and aerodynamic behavior of the muffler. Related Articles | Metrics

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Effect of Inlet and Outlet Locations on Acoustic Attenuation Characteristics of Elliptical and Oval Expansion Chambers FANG Zhi .J I Zhen-lin 2011, 31(4): 160-164.  DOI: 10.3969/j.issn.1006-1355-2011.04.038 Abstract ( )   The acoustic modes of elliptical and oval expansion chambers are calculated using the finite element method, and the effects of inlet and outlet locations on the acoustic attenuation characteristics of the expansion chambers are studied. The numerical results show that the first propagation mode for the concentric expansion chambers is the third mode. The effect of the third mode can be eliminated by locating the outlet on the nodal line of this mode, and with this method the range of plane wave can be expanded and the acoustic attenuation performance of the expansion chambers can be improved. For the expansion chambers with offset inlet and outlet, the first mode is excited and the three-dimensional wave effects appear at lower frequencies, and the acoustic attenuation performance becomes poorer in the middle frequency range. Related Articles | Metrics

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Sound Insulation Performance Analysis of Magnesium Honeycomb Panel GU Xiu-e;;QUAN Gao-feng;;SHI Lin 2011, 31(4): 165-168.  DOI: 10.3969/j.issn.1006-1355-2011.04.039 Abstract ( )   The sandwich panels made up of AZ31 magnesium alloy sheet with the AZ31 magnesium alloy honeycomb core and AZ31 magnesium alloy sheet with the magnesium-aluminum honeycomb core were prepared respectively. Their sound insulation properties for different structural parameters of the honeycomb cores were measured. It is expected that the vibration and noise of the floor or wall of the vehicles can be greatly reduced if these honeycomb panels are applied, the riding comfort can be greatly improved and the energy efficiency can be raised. So, these panels have practical significance in transportation engineering. Related Articles | Metrics

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Analysis of Vibro-acoustic Property and Optimization of Air Filter GUO Fu-yang;CHEN Jian 2011, 31(4): 169-172.  DOI: 10.3969/j.issn.1006-1355-2011.04.040 Abstract ( )   Acoustic-vibration coupling property of an air filter is analyzed by LMS Virtual lab in this paper. The radiation noise by the coupling effect of the filter’s case and the interior acoustic chamber is computed when the air filter is excited by the simulated engine force. Contribution of structural modes to the radiation noise is analyzed. To improve the structural property, the configuration of the air-filter’s case is optimized according to the analysis result using the Optistruct module of Hypermesh, and the optimal scheme is given. Related Articles | Metrics

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Analysis and Design of Rapier Loom’s Feedforward and Feedback Tension Control System SONG Ya-nan;XU Rong-hua;WANG Qin-ruo 2011, 31(4): 173-177.  DOI: 10.3969/j.issn.1006-1355-2011.04.041 Abstract ( )   Based on the analysis of noise source and noise characteristics in rapier loom’s tension-control system, the design method of the control structure and controller is proposed. On the base of the concept of the degree of control difficulty, a suitable analog low-pass filter is chosen for filtering the high-frequency signal and random noise. While in the periodical low-frequency noise processing，the frequency spectrum analysis is used to determine the period of the noise and the coherent mean method is used to obtain the signal. Then, the periodical vibration noise behind the analog low-pass filter can be estimated. Based on the estimation of the noise, a digital filter and feedback compensation are designed and employed to improve the control system’s performance. On the other hand, this method is also used to estimate the periodical vibration noise in front of the analog low-pass filter, and the digital filter and the feedforward compensation are designed to improve the control system’s performance. The effectiveness of the analysis and design methods is verified through matlab programming and simulink simulation. The analysis, methods and results proposed in this work provide some data for actual rapier loom’s tension control filter and controller design. Related Articles | Metrics

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Acoustic Enclosure with Intelligent Controllable Noise Insulation LIANG Sen;MI Peng 2011, 31(4): 178-181.  DOI: 10.3969/j.issn.1006-1355-2011.04.042 Abstract ( )   Based on acoustics theory, the acoustic pressure field varying with the gas pressure change in an acoustic enclosure with sound-absorption treatment is formulated. Combining the acoustic enclosure technique with PLC technique, an intelligent acoustic enclosure is designed for the machines which are always working under dynamic loads. The noise insulation of the enclosure can be adjusted according to the variation of noise radiation energy by changing the vacuum of the acoustic enclosure. The noise insulation is controlled by a system which consists of transducer, PLC, servo motor, etc. This acoustic enclosure has many advantages over the traditional one. It can isolate the noise with different frequency bands and is easy to realize automation and intellectuality. The validity of the method and design is confirmed by a more-than-one-year application in a gas compressor workshop. Related Articles | Metrics

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Study on a Special Noise Isolation Structure Based on Standing Wave Theory GAN Xiao-ye;ZHAO Xin-guang;LIU Xin-hong;CHEN Chang-zheng 2011, 31(4): 182-184.  DOI: 10.3969/j.issn.1006-1355-2011.04.043 Abstract ( )   A new sound isolation structure is designed on the base of stationary wave theory for sound isolation processing of the relatively small noise sources with their waves propagating in narrow paths as in the ducts. This design is confirmed by an in-situ experiment. Results show that this structure is effective in sound absorption, and can eliminate the adverse impact of the stationary wave on machine itself. Related Articles | Metrics

9.振动噪声测试技术

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Research of Hybrid Sound Absorption Based on Characteristic Impedance ZHU Cong-yun;LI Ming-li;JIANG Chun-ying 2011, 31(4): 185-189.  DOI: 10.3969/j.issn.1006-1355-2011.04.044 Abstract ( )   Aiming at the character that the effect of the active sound absorption is very good for low frequency acoustic wave, and poor for middle and high frequency sound wave, a new hybrid absorption system is proposed in this paper. This system consists of a layer of absorbent material and a movable rigid wall. The speed of the movable rigid wall can be adjusted in order to make the acoustic impedance of the absorption material match the acoustic impedance of the air, so that the absorption coefficient of the hybrid system can reach the maximal. A numerical calculation and an experiment are carried out for the case of normal incident plane wave. Both results show that the absorption coefficient of the hybrid system can reach 0.8-1.0 in the frequency range of 100-2 000 Hz, but the absorption effect of the system has not been improved very much when the frequency of the sound wave is higher than 2 000 Hz. Related Articles | Metrics