Using frequency and modal analysis to attenuate low frequency waves

摘要

The paper analyzes the response of structures and machinery to low frequency vibration (LFV) such as low frequency waves (industrial seismic waves) generated by different machines, technological processes, etc. The principles of the analysis can be applied for different kinds of excitation (stationary -deterministic, random and non stationary - continuous and variable). Some sources, as a result of human activity, for LFV and their subsequent low frequency waves (LFW) were investigated and analyzed. The goal was to determine the Eigen frequencies and Eigen modes of the measured structure and/or machinery not only by identifying sources of vibration but also applying operational modal analysis which is important in designing suitable modal damping. The operational frequency spectrum with Eigen modes of the structure and/or machinery is compared by means of frequency and modal analyses. Through modal damping, levels of low frequency noise may follow, and the transmitted LFV can be the reason why resonance or excitation of the Eigen modes occur. In the conclusions, the measured results of the LFW caused by a vehicles combustion engine is analysed as well as its effect on the cabin of the vehicle. Similarly electromotor resonance is investigated as well. The results of the frequency analysis, and the resulting measurements show the most effective way to attenuate high energy LFW.