A simple method called Numerical-Axis-Method for establishing the mathematical models of the common mass-spring-damper systems was put forward. In establishing the mathematical model, a numerical-axis parallel to the system was built, and the displacements of the spring or the damper were translated to the rational numbers which were marked on the numerical-axis. Then the magnitude and the direction of spring force or damping force applied to the corresponding mass was determined by comparing the two rational numbers mutually. The application of this method on establishing the mathematical models of mechanical vibration systems was expatiated through a single degree-of-freedom (DOF) system, a double DOF system and a multi-DOF system. The results show that this method was very efficient in establishing the kinematic differential equations of the mass-spring-damper systems.

Secondary path modeling is a key issue of adaptive active noise control (AANC) system. An impulse response measurement based on time stretch pulse (TSP) signal is used in this paper. TSP signal has the characteristics of distributing the pulse energy in a period of time. The impulse response function of the tested system with TSP signal can be reconstructed by gathering the scattered energy in the response signal. The method is applied to secondary path modeling, and 20dB and 14dB noise reduction is respectively obtained in simulations and experiments. The results show that the secondary path modeling method based on TSP is simple, accurate and very suitable for practical ANC engineering test.

The influencing factors of noise and vibration of vehicles are material, tire pressure, vehicle’s structure, road conditions, and so on. This paper analyzes the influence of the inflation pressure of the tire on the noise and vibration of the vehicles. According to the experimental data and theoretical analysis, tire rigidity and natural frequency will increase with the rise of tire’s inflation pressure; suspension and auto vibration will vary evidently with the change of the tire’s pressure; the tire’s pressure has some influence on air pumping noise; the influence of the tire’s pressure on tire’s noise level is low and irregular; the rise of the tire’s pressure will decline the capability of tire’s vibration absorbing and increase the sense of vibration and shock, and will also reduce the riding comfort of the vehicle. The reasonable tire’s pressure is important for reducing the noise and vibration of the entire vehicle.

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.

A survey on the research of the unbalanced magnetic pull(UMP) in the motors is given in the paper. The mechanism of UMP is analyzed and summarized. The developing status of the research of UMP, especially the nonlinear UMP, is also introduced. The ways to preventing and reducing UMP are also summarized. Finally, the future research orientation of UMP is also discussed.

With the rapid development of wind power technology, faults of wind turbine happened frequently. The research on the safe operation and the fault diagnosis of the wind turbine has become an important content in wind power technology development. The domestic research on the fault diagnosis technology of wind turbine is still in the initial stage and focus on the gear box a few in rotor misalignment fault. In view of these problems, the acquisition of vibration signal on the abnormal operation wind turbines was completed by the vibration test system and rotor misalignment fault signal was detected by analyzing the vibration signal in time domain and frequency domain. It will make contribution to rotor misalignment fault diagnosis.

Aiming at the vibration signals of abnormal sound from cylinder's head of motorcycle engine, characteristic values of the abnormal sound of each cycle are computed in timedomain using statistical functions. Comparing these characteristic values with the frequency spectrum of the normal engine, the characteristic frequency of the abnormal sound is found. Through the order analysis, the energy distributions of both normal and abnormal vibration signals of engines are studied. And the energy differences of the vibration signals of various orders are analyzed. The results show that these methods can identify abnormal sound of the cylinders head effectively.

The frequency-domain analysis is the most important and applicable signal processing technology in fault diagnosis for machinery. In the literature, a number of frequency-domain-based methods have been applied to detect faults in machinery and each method has its special features. Therefore, selecting appropriate method plays a pivotal role in inspecting defects based on vibration signals. Characteristics of fault-caused vibration signals and frequency-domain-based methods are summarized in this paper using representative examples, so as to establish a rule of selecting appropriate signal methods of extracting vibration features for different mechanical equipments. The results can be used to improve the precision and reliability of many kinds of fault diagnoses for key components in different machinery.

Porous sound-absorbing materials are widely used because of its high sound absorption coefficient and wide absorption frequency range. In this paper, a model of sound absorption materials is adopted, and the design parameters are computed. The influence of porosity, diameter of holes, thickness and structure of the material on its sound-absorbing property is analyzed. This work provides a reference for the development of new sound-absorbing material.

The eddy current damper has widespread application prospect in vibration control field which has advantages of non-contact and non-mechanical wear etc. A novel lateral eddy current damper was uesed for lateral vibration suppression of rotating disk. The electrical model of eddy current damper was established based on electromagnetic field theory, the radial and axial force of formulas were deduced combined with disc structure parameters. The relationship of the damping force and current, clearance(the distance between the end face of damper coil and disk) and the speed of disc was simulated and analyzed. The study laid a theoretical foundation for the implementation of vibration control and practical application of lateral eddy current damper.

Least-squares complex frequency-domain (LSCF) method developed to be implemented in modal parameter estimation recent years. An expect result was received either in the system of weak damping or heavy damping. An User Interface was designed based on Matlab consisting of the LSCF method. Different parameters were set based on different coefficient matrixes and solution modification of the pole of the system was given. A test was used to validate the consistency of the different coefficient matrixes and that the User Interface was correct.

Through the experimentation of the noncrystalline alloy transformer , theoretical analysis and calculation of its finite element model ,and analyzing and exploring the vibration and noise source of the transformer, we choose the signal of the transformer vibration and noise to experiment in different frequency, receive datas ,analyze them and finally draw a conclusion that the experimental way and theoretical way have the same result that the transformer noise is not from current noise ,but from the up clamp structure which accepts prompting vibration radiating noise . That conclusion has a factual instructive suggestion for reducing transformer noise further.

A rational shafting alignment for a real vessel is carried out. The rigidity of bearing support and vessel deflections are taken into consideration. Their influences on the results of shafting alignments are analyzed to provide a deeper comprehension and theoretical reference for vessel designers.

The drum of a washing machine rotates at a high speed during dehydration work, while the clothes in the drum rotate together with the drum, yielding pressure on the drum wall which causes the drum to deform. With software Pro-E and ANSYS the finite element model of a washing machine drum with its support is established. Dynamic analysis of the drum structure in the case of dehydration work is carried out. The natural frequencies and vibration modes are obtained. The critical positions and the critical rotating speed are found. Some improvement suggestions for the washing machine drums are esented.

In this paper, several wavelet denoising methods are compared and analyzed. On these bases, a new threshold function is constructed. The improvement of threshold selecting is made. Simulation experiment of signal denoising is carried out using MATLAB software. The advantage of improved wavelet denoising method is demonstrated, and better denoising effect is gained.

In this paper, the dynamic characteristic of Roots blower's shell is analyzed by the ANSYS code. The natural frequencies and the vibration modes of the shell are given. The output of computation shows that the natural frequency of the shell is higher than the fundamental frequency of the rotor system, and the vibration modes of the shell structure are mainly bending, twisting, and their combination. The dynamic analysis of the shell may predict the faults in structural design, and provide some scientific basis for reducing the structural vibration and the noise of the Roots blower.

By using operational deflection shapes (ODS) technology, the vibration of a tilt open drum washing machine （7-600Hz）during dehydration was investigated. Combining with the noise measurement results, the correlation between vibration and noise during dehydration was preliminary discussed. It showed that, the vibration of the machine excited by the unbalance force of the running parts and the electromagnetic force of the electromotor, and the lowfrequency noise was closely related to the vibration. The noise level of both left and right sides were higher than front and back sides. To decrease the noise level, it can modify the frequencyresponse of the machine.

In view of the controversy of ride comfort evaluation methods of domestic and international, the characteristics, differences and scope for each evaluation methods were analyzed. The integration of level of analysis and fuzzy is the typical subjective evaluation method. Then four object methods were described which were absorbed power method, the overall ride value method, VDI2057 (2002) and ISO2631 (1997). Finally several new subjective and objective comprehensive evaluation methods, including automotive integrated vibration comfort, fuzzy evaluation method and irritability rate analysis were introduced. The study found that every method is work, but the standard varies. The comprehensive evaluation methods can be better integrated to achieve the vehicle ride comfort evaluation, which may be the focus of future research directions.

Testing and evaluation of noise are important work for the quality controlling of security inspection equipment. In this paper, some indexes for noise evaluation are analyzed and compared one another. As an example, the characteristic of the noise radiation distribution in the EI10080 security inspection equipment is analyzed experimentally. The method for testing and evaluation of noise of security inspection equipment is proposed by analyzing the sound pressure levels of noise at two prescribed points. Results of testing show that this method is easy to handle and has a high precision.

The transmission loss is one of the important characteristics to appraises the muffler performance. But in the experiment, it should been pay attention to the acoustic source stability and sound wave reflection questions.In this article summarized some differences which the insertion loses and transmits loses, Simultaneously pointed out the merits of application transmission loss test noise elimination performance，And for avoided the sound reflection proposed one new transmission loss test way. Discussed the transmission loss value change situation when the muffler be inputed different intensity sound pressure, which through the massive experiments.

A multi-input and multi-output unbiased frequency response function (MMUFRF) estimation is put forward based on the feature that the mean of the incorrelate signal CSD (Cross Spectral Density) tends to zero. The proposed method is realized by MATLAB programming. Two-input and four-output test is carried on using the dynamic signal test systems and its MMUFRF is acquired by MATLAB program. Meanwhile, numerical simulation of the frequency response functions is made by means of finite element method. The simulation results show that the proposed MMUFRF can correctly estimate the frequency response functions of real structures.

Based on Simulink software, the simulation model of a nonlinear vibration system with bilinear restoring force is established and analyzed. The result shows that Simulink software can simplify computer processing and raise the reliability of computation. The displacement, speed and acceleration responses in the time domain can be gained more easily.

An active absorption method using piezoelectric material is proposed in this paper. In this method, a piezoelectric ceramic is used as the absorption material in the active absorption system. Two microphones are placed in the front of the piezoelectric ceramic with equal distance from it to measure the incidence plane wave and the reflecting wave. The voltage is applied on the surface of the piezoelectric ceramic in order to eliminate the reflection wave. Finally, simulation of the active absorption control is carried out by means of the MATLAB code for the incidence plane wave with different frequencies. Results show that the proposed method is effective and feasible.

Using noise and vibration analysis system, the transmission system noise and vibration of a traction motor were tested, and the characteristics of the noise and vibration were analyzed. It is concluded that the noise level increases with the rotation speed increasing mainly in the frequency range near 800 Hz, and noise of MIC02 is higher than the noise of MIC01; gearbox vibration is bigger than motor vibration. This work provides a reference for noise and vibration reduction design of transmission systems of traction motors.

With the development of cryogenic technology, cryogenic liquid products are important in many fields. As representative for fluidconveying tools,pipes are widely used in industry fields. But fluid structure interaction in working liquidfilled pipes, and the vibration characteristic in cryogenic fluidconveying pipes, which have been extensively studied in the academic and engineering communities. In this paper, the typical achievements in the research field were summarized and reviewed.

The problem of vibration and noise of the PMSM have been a difficult dilemma, it makes the system unstable and sometimes present the chaotic phenomenon. Advanced control method can depress vibration and noise and improve the control performance. the paper gives a design of global nonsingular terminal sliding mode controller for BLDC Motor which can makes the control system is insensitive to any disturbance. The simulation results prove the validity of the controller, and by compare with classic PID control, it has beed proved that the global nonsingular terminal sliding mode controller is more effective.

The characteristics of an urban 110kV indoor substation and its noise are described. Its noise control methods are briefly analyzed. An example of noise control of a typical urban 110 kV indoor substation—Shanghai Anshan 110 kV substation, is introduced. It can be used as a reference for similar projects.

There is some strict boundedness in acoustical prediction formulas of sound barrier recommended by some documents. The boundedness will limit applicable range of these formulas. Therefore some suggestion was proposed to improve acoustical prediction formulas of road sound barrier. The suggestion includes: (1) A universal method was introduced using the image source and image receiver when a reflect ground was considered; (2) Several corresponding prediction formulas were made when the source and receiver all are near a rigid ground, and for pulse point source, the attenuation formula was represented separately to express attenuation limiting value in an actual barrier when Fresnel number N>10; (3) The reflect sound reformation of a double barrier also can be calculated using the image source method.
The examples discussed in this paper not only prove that the suggestion is reasonable, but also provide some interested conclusion, such as (1) The reflect ground will increase sound pressure at a receiver, and decrease attenuation of barrier. When the source and receiver all are near a rigid ground, sound pressure at a receiver will increase 3 dB without a barrier, and 6 dB with a barrier, the attenuation of barrier will decrease 3 dB; (2) The reflect sound reformation of a double barrier almost are same with or without the reflect ground, and the reformation will decrease with increase of the absorption of barrier surface toward source.

To exist inaccurate damage location for current flexibilitybased method for damage localization，a new damage index based on the orthogonal relation between stiffness matrix and flexibility matrix is presented combining with the matrix perturbation method and the finite element method. It can obtain accurate damage location using several order modal parameters. The effectiveness and superiority of this approach is verified by a numerical simulation for the plane truss，and it will be possibly used on damage localization for complex structures.

The Dynamic analysis models of the airconditioner outdoor unit and the compressor refrigeration system are established by means of the finite element method (FEM). The modal analysis is carried out by ANSYS code. The impact of the piping on the compressors structural vibration using the rubber pads with different hardness is obtained. The natural frequency and vibration mode of the system are computed. Then the most suitable stiffness of the rubber pads can be used to reduce the compressors structural vibration. The vibration and noise of the pads with various stiffness are measured. The vibration velocity curves are plotted and the spectrum analysis is carried out. With the appropriate measures for forecasting the vibration and noise reduction, the design scheme may be more scientific, feasible and economic.

In order to reduce the transmission’s squeak, the main noise source of the transmission is recognized by the NVH testing. By analyzing the dynamic actuation of gear clusters, it is confirmed that the mesh impact among gears is the main actuation source of the squeak. Then, by reducing backlash and increasing contact radio, the optimization of the gear clusters is carried out. This method is proved useful in reducing the transmissions squeak induced by the gear meshing.

Many noise source identification measures show that the source of the abnormal noise of an idling truck is the air compressors induction noise. Based on this, the expansion muffler and interference muffler are designed on the inlet duct of the air compressor. The acoustic finite analysis for the inlet system including muffler, air cleaner and the inlet duct of the air compressor and the engine shows that the muffler has remarkable transmission loss. Base on these, the samples for the expansion muffler and the interference muffler are made and tested in the truck for verifying noise control effect. Result shows that the designed muffler can control the noise effectively and the interference muffler is better than the expansion one. Considering the shortage of the designed interference muffler and the characteristic that the air compressor shares the same inlet system with the engine, an engineering design for the interference muffler is present. The acoustic transmission loss and the noise control of the engineering one are also notable. Although the engineering interference muffler is a litter worse than the interference one, it avoids the shortage of the interference one that the duct is too long to choking. Lastly, an intake time testing for the gas storage is done with the engineering interference muffler, though the intake time is a bit longer, it is still better than the national standard.

Planetary gearsystem is widely used in mechanical equipment which transmits motion and power. But its fault diagnosis is somewhat difficult. In this paper，by means of the traditional edgefrequencysignal recognition technique，the fault of a threestep planetary gearsystem is measured and analyzed. The analysis shows that the axis of the solargear of the first step deviates the theoretical axis, thus the axes of the planetary gears of the first step deviate their theoretical axes also. The eccentricity of these axes leads to large vibration and noise. In addition, modal analysis shows that the resonance of the planet gears happens due to the excitation of the large meshingimpulsion. Finally, the structure of the planetary gear system is improved, and a 2.5dB(A) noise decreasing is obtained.

Based on digital video technology, video image vibration measuring system is designed with the general USB digital camera and PC as its hardware. Meanwhile, the first-order modal parameters of a simply supported beam with concentrated masses applied are identified. Vibration video acquisition and image edge detection procedures are programmed in the MATLAB environment. The displacement-time curve of the beam vibration is obtained. Modal analysis is applied to determine the natural frequencies, the damping ratio and the vibration modes of the simply supported beam. The testing results show that this testing system is feasible for realization of the vibration test for low-frequency structures.

In order to investigate the noise level of different line forms of 350 km/h high-speed train, the noise intensity at different distance from the Beijing-Tianjin Inter-City high-speed railway was tested and analyzed. The result indicates that the noise level radiated by the train reaches the highest at 60m distance. Then the noise level decreases with the distance increasing. The result is significant for noise reduction design of the express train-sets.

The Gaborexpansionbased time frequency filtering is employed to process measured signals before conducting parameter identification. With Gabor expansion, the local characteristics of a signal can be shown in the timefrequency domain, according to which the properties of responses are acquired and the response signals can be filtered by elimination or interception. This technique can be applied to both stationary and nonstationary signals. Attribute to this technique, more information about the signals and systems can be gained, such as the distribution of natural frequencies, energy assemble functions, quantity of properties contents in each channel.

Employing the frequency hardening coefficient in the nonlinear dynamic system consisting of mobile hard disks with rubber isolator, a set of nonlinear differential equations for this system is established. The corresponding model for numerical simulation is constructed. The dynamic responses for different pulse durations and pulse magnitudes of acceleration are computed with this model. The influences of pulse signal parameters on the isolation effect are analyzed and discussed. Theoretical analysis and numerical simulation show that the model presented here is more reasonable than the traditional linear dynamic model. Furthermore, this model is simple and convenience for tation. It can be used to determine the natural frequencies of nonlinear vibration-tion system effectively.

Windings’ deformation is one of the most frequent faults for the power transformer. Based on the vibration frequency response analysis, this paper proposes a correlation coefficient of vibration frequency response curve in order to more effectively detect the windings deformation. In the experiments, the vibration frequency response method is used to detect the states of largescale power transformers windings which are manmade fault. The results analysis shows that this correlation coefficient is sensitive to the windings deformation.