Noise And Vibration Analysis And Control Of Crane Cabs Based On SEA Theory

In recent years, people have paid more and more attention to the noise-related environmental problems in that noise pollutions can seriously affect people’s daily lives all the time. In order to have a quiet and comfortable living environment, the upper limits of noise levels are clearly defined in different industrial areas, including the port machine industry. In port machinery industry, workers usually need to work eight hours or more in the crane cab per shift, so the health of workers is closely related with the indoor noise environment. The commonly used techniques of noise-and-vibration analysis and control are mostly the finite element methods and/or boundary element methods, especially in the domestic port machine industry at present. However, as the broadband of crane cab noise source excitations is usually distributed from a few hertz to several thousand hertz, and the resulting modal densities of the cab systems can be very big for the frequency range of interest, the results from the finite element methods can be very uncertain and lack of confidence. Besides, the computational cost of finite element analysis can be very high.Statistical energy analysis (SEA) is a statistical method in which subsystem energy responses are taken as the few of main variables. Statistics addresses the using of the statistical ensemble of known dynamic parameters distributions to describe the dynamic system of interest. As a result, all SEA parameters are described by their probability nature. It is the average of the various modes of vibration on time, space and frequency bands of interest. The statistical energy response of each subsystem is the main variables, and other dynamic variables, such as displacements and sound pressure levels can be obtained from the energy response variables. Most importantly, it is addressed that SEA should be considered more as a kind of methodology for solving higher frequency noise and vibration problems, rather than a particularly specified technique.This dissertation is supported by the National863Project and Shanghai Zhenhua Heavy Industry (Group) Co., Ltd. For the quay crane cab, it was found that the noise and vibration levels of the cab are too high. To solve the problem, first, lots of fundamental research on statistical energy analysis were carried out, especially on the power balance equations between SEA subsystems and the SEA main parameters (such as modal density, damping loss factor and coupling loss factor); Secondly, some basic theory of acoustics was revisited; and thirdly, a method to solve the noise and vibration of the quay crane cab was proposed based on statistical energy analysis. The new SEA model combines the full-band acoustic simulation software VA One. By establishing the acoustics analysis model of quay crane cab, a series of vibration and noise analysis was conducted under the guidance of the statistical energy analysis and acoustic theory. This then followed the experimental measurements on improving the effective sound insulation and isolation levels in order to reduce the quay crane cab indoor’s noise and vibration levels according to the SEA predictions. Finally, the technical indicators of National863Project were successfully completed with various methods suggested for solving noise and vibration problems of the domestic port machine industry. In this dissertation, a new technique was proposed which combines SEA theory and VA One software. Moreover, it is expected that the new technique can provide some useful information on solving practical noise and vibration problems for domestic port machine industry.