the Box-Behnken design and response surface method were applied to optimize the parameters of noise barriers. The height, length and initial stake of noise barrier were studied as arguments, while the insertion loss of three sound-sensitive points, construction cost as variables. Quadratic equation models were developed to express the functional relationship between arguments and variables. Optimization parameters of noise barrier were obtained by Minitab analysis, basing on the goals of acoustic environmental standard in sensitive area, as well as minimization of construction cost.

Based on investigation of built highway noise barriers in Jiangsu province, the effect of several factors, including equivalent frequency, traffic flow, etc, on insertion loss of highway noise barriers were analyzed, and the revision was carried out. The results show that the sound source model reflecting characteristic of traffic noise is the key to assess acoustic performance of noise barrier. Meanwhile, there were some construction defects on a few of noise barriers, leading to sound leakage and poor acoustic performance.

Fiber glass has been widely used for automotive exhaust muffler to achieve good performance of noise reduction from the middle to the high frequency range. In this paper, the classification of the raw material and component of domestic fiber glass was studied experimentally. The results indicated that the domestic fiber glass can completely meet the requirements of acoustic attenuation performance.

The line modal testing was carried out for analyzing the modal parameters of the body structure of high speed train. The LMS test.lab, a famous noise and vibration test system, was used for data collection and processing. Based on the theory of modal parameter identification and the modal testing method under environmental excitation, the PolyMax modal extraction method was used and the elastic modal parameters and the corresponding vibration modes of the first three orders of the train’s body were obtained. This work may provide a reference for body structure optimization.

Noises are artificially added to a real Transiently-Evoked Otoacoustic-Emission (TEOAE) signal to stimulate the collected TEOAEs signal. Then, the stimulated signal is denoised using traditional denoising method and wavelet transform method, and the results are analyzed. The suitable wavelet parameters for TEOAEs are found to improve the correlation ratio and the signal-to-noise ratio of the results, and to reduce the inspecting time.

In order to overcome the interference of environmental noise and improve the quality of EMD, the wavelet method is used to eliminate the noise signal. The correlation coefficients are applied to remove the pseudo components. And then, the random decrement method and ITD method are used to identify the natural frequency and damping ratio of train’s floor. Compared the identification results with those from LMS commercial software, it is found that the relative error of frequency is less than 5%, the relative error of damping ratio is less than 7%. This shows that the method has high precision of identification.

The structure of High-speed vehicle is complex, though simulation to obtain structural properties on the current computer simulation is still difficult.Modal testing is used to obtain dynamic characteristics of the structure. This paper describes a test method for structural characteristics, and its realization of the basic algorithm. Multi-excitation method is to be used and the measuring point for the minimum non-resonant component of the objective function of the adjustment force method is to establish. Simulation results show this method is simple, less post-processing work,and high reliability.

The welding seam of the upper tensilerods safety hangers of GQ70 light oiltank truck may split easily during the operation. But the safety hangers usually bear small load, and its failure is not a material strength problem. The modal test with hammering method is carried out at some key portions of the safety hangers. Using experimental modal analysis method, the modal frequencies of the hangers are found. Through comparative analysis, the cause of splitting of the hangers is found, and some suggestions for repairing are proposed.

The problem of noise pollution and energy waste of a boiler room in a residential area of Dalian city is studied in this paper. The causes which induce excessive noise and energy waste are investigated by analyzing sound source and propagation path of the noise. Then a method, that can reduce both internal and external noises of the boiler room and can save energy, is proposed. A good effect in engineering application is obtained.

Cantilever rotor is the key component part of mechanical equipment. Based on the failure mode of dynamic response of the cantilever rotor, the ensitivity factors which affect structure reliability, such as load, size of structure, properties of materials, are analyzed. The utmost equations of the cantilever rotor in both static and dynamic states are built. Each equation is linearized at the average point by Taylor Expansion scheme. The reliability of structure is calculated by employing the theory of the primary second moment. The reliability results of considering and ignoring the inertial force respectively are compared mutually and analyzed. Then, an effective reliability analysis method for cantilever rotor is established.