Unsteady noise test technology and time-frequency refinement analysis methods were used to investigate the cutting noise characteristics of the larger cold saw. The noises in different time-intervals in sawing process were tested. Then, by eliminating the background noise, the cutting noise characteristics were analyzed by the time-frequency refinement analysis method. The results show that the sawing sound field has higher sound pressure level, the radiation frequency has stronger time-varying performance, the sound energy is focused on the lateral direction of the cutting, and high-frequency is very obvious in the noise. This work may provide a technical support for noise test, sound field characteristics analysis and noise control of some complex machines such as fans, compressors, etc.

The auto-regressive(AR) model of exhaust noise in diesel engine’s seven operating modes about the valve train was established. The auto-regressive parameters were regarded as the characteristic vectors to build the fault diagnosis model which was based on extreme learning machine. The proposed method was also compared with that of BP neural network, RBF neural network and support vector machine. Experimental results show that exhaust noise can be used for fault diagnosis in diesel engine’s value train. The classification accuracies of above four different intelligent methods are all higher than 95%. But the method of extreme learning machine has advantage apparently in training rate.

The dynamic equation of a 2-dimentional hypersonic wing was derived by using the modified third order nonlinear piston theory. Both linear and nonlinear flutter boundary conditions were obtained through Hopf-bifurcation theory and directive numerical method respectively. The simulation results show that the effects of nonlinearities can delay or precede the appearance of limit cycles oscillations according to the system parameters.

The marine equipment includes seawater marine pump, drainage pump, screw pump, hydraulic pressure pump, air-conditioning chilled water pump etc. These pumps work with various forms including rotation, reciprocation, meshing etc., and vibrate with different frequency characteristics. In this paper，the vibration levels, characteristics and causes of different rotational marine pumps were analyzed. Some measures for vibration reduction were proposed and applied to the improvement design of some pumps. The results of testing showed that the vibration level of these pumps was reduced as the expected.

A simplified multiple DOFs lumped-parameter elements model is established to study the dynamic properties of vibration path in powertrain-vehicle’s system in high frequency range. The relationships among isolator, interface velocity and each component’s mobility are derived. The main parameters influencing the dynamic properties of the vibration paths are determined by component’s parameter study. Finally, effective methods are proposed to perform dynamic design of the powertrain-body vibration transfer system.

A method for vehicle interior structure noise design in the middle frequency range in early stage of development is proposed in this paper. The dominant cause of structure noise for main transfer path is determined according to the simulation result of the “Digital Mule” vehicle model and the reference vehicle model, and then NVH performance targets for corresponding subsystems are established. The overall target is finally reached by achieving subsystem targets. An example for powertrain induced noise confirms the efficiency of the proposed method.

By using hammering pulseinspirit method, the experimental modal analysis of a refrigeration compressors shell is carried out. The fundamental modal parameters, including natural frequencies (1kHz 4kHz), damping and mode shapes, are estimated and identified. The intrinsic vibration characteristic of the compressors shell is obtained. Based on the experimental modal analysis, the dynamic characteristic of the shell structure is investigated. The results show that the main modal shapes of the compressors shell are essentially the outwardexpanding and inwardcontracting vibrations. The main cause of noise radiation is the intrinsic vibration of the shell. The results of the experimental modal analysis can provide a useful reference for vibration and noise reduction of the compressors.

Based on modal control method, the vibration modes in an object test are directly controlled. The aim of the experiment is to reduce the vibration of the base of the object. The experiment result shows that the modal vibration shape can be controlled using this method, and the bases vibration can be reduced.

The method of noise analysis of aircleaners with random transfer function is presented using matrix perturbation theory, matrix calculus, Kronecker algebra and generalized second moment method. Considering the uncertainty factors of the atmosphere, the random response of the aircleaner is described clearly in the time and space domain, and the decibel (A) value of the former second moment of random response at the sound outlet of the aircleaner is obtained.

Using the statistical energy analyzing method (SEA), a model for analyzing the marine floating raft isolation system is established. The vibration isolating effect of the raft isolation system is measured and analyzed by means of the Vibration Level Difference method. Comparing experiment result with theoretically estimated value is civen out. It shows that this method can meet general need of engineering design.

The factors which influence the wave velocity in hydraulic media are analyzed and computed. It is presented that in the high pressure system and oilgas doublephased state the previous assumptions for compressive wave velocity formula in hydraulic media are not true any more. Thus, a new estimation method is necessary. In this paper, a new nonintrusive measurement method is proposed. In this method, the pressure gauges are installed at two different positions on the pipeline to measure the time difference when the compressive wave reaches. Therefore, the wave velocity can be determined. The randomness of elastic modulus under the condition of oilgas doublephased flow is studied in highpressure fluid system. The results provide references for simulation, design and management of hydraulic systems.