Aiming at the issue of threshold function setting by using wavelet transform signal denoising, an improved method of threshold function based on the classical method of soft and hard threshold function denoising was presented. After this improved threshold function method and the maximal overlap discrete wavelet packet transform were combined, a wavelet denoising method of improved threshold function was obtained. Simulation results obtained from Matlab software indicated that this method can improve signal-to-noise ratio(SNR) of the reconstructed signal, remove the noise effectively, and reserve the main characteristics of the original signals. So, it is better than the traditional methods. This method has a practical significance in application of stock denoising.

Vibro-acoustic analysis methods and related software for noise analysis of offshore platforms, FPSO structures, etc. were summarized and discussed. It was elaborated that there are two paths in transmission-airborne transmission and structural borne transmission, and both of them should be considered in the analysis. Moreover, it was indicated that the fast multi-pole boundary element method would play an important role in vibro-acoustic analysis in the future.

The dynamic model of vehicle’s active suspension for steering analysis is established. The EPS model, tire model and road-condition input model are introduced. Fuzzy neural network control method is used to design the vehicle’s active suspension and the integrated EPS control system. According to the changes of the body posture of the vehicle, the active force and the EPS assistant torque of the actuator of the active suspension system can be adjusted dynamically. The simulation and analysis are carried out for different steering-wheel angle input. The results show that compared to the uncontrolled suspension and steering system, the vertical acceleration peak and standard deviation of the active suspension and the EPS integrated control system are decreased by 40.94% and 26.06%, and the peak and standard deviation of transverse angular velocity of the vehicle are decreased by 6.24% and 48.15%. Thus, the vehicle body’s vibration is suppressed effectively, and the ride-comfort and handling stability are greatly improved.

The finite element model of a vehicle body was established based on a kind of vehicle at first, and the computational modal analysis was conducted. Computed results was compared with experimental ones, the validity of the finite element mode was verified. Based on the results of modal analysis, the improving method of the vehicle body’s vibration and noise control was given out. Then the vehicle structure was improved on the model and the vehicle interior noise of the improved vehicle structure was computed. The result indicated that the improving method could control the interior low frequency noise of the vehicle.

A commercial vehicle is chosen for study. The interior noise is tested based on national standards. According to the results, the distribution and the spectrum characteristics of the interior noise are analyzed.