Abstract
This article represents method for analyzing noise-vibration values measured from gearbox of light trucks designed and made in Vietnam in the laboratory. The results obtained while measuring from sensors in different measuring modes are acoustic pressure values as per time domain treated by the DasyLab 7.0 software. Since the results are provided in the form of acoustic pressure values as per time domain, use of these results as grounds shall not meet the requirements as well as expectation of noise-vibration measuring experimental doers. In order to obtain more explicit and visual, the following steps should be taken: - FFT analysis (Fast Fourier Transform): Each vibration signal is usually a combination of many harmonic motions; Fourier analysis allows separating every single harmonic emotion as such: - Octave: With octave analysis, we can divide the horizontal axis as per octal system so as to limit axial parameters, and then get the value of the frequency range with the highest noise compared with its criterion. - Envelope: Envelope analysis forms vibration envelope contours of elements in the emerging system. Observation the repetition of frequency (f) shall help analyze, predict, and consider which frequencies of the elements can be repeated. - RMS (Root Mean Square): Takes mean value of a vibration in different measuring modes. From this value, the Excel software is used to establish noise-vibration value table, diagrams to demonstrate vibration of experimental noise-vibration measuring modes. - Matlab 7.1: Uses value tables from Excel in the conversion part from RMS, the Matlab 7.1 software is used to program and build Noise-Map for the experimental gearbox. With Noise-Map, we can demonstrate noise-vibration in experimental modes thus helping identify, infer noise-vibration results in the most overall and visual manner.
Keywords: Gear Box, Noise-Vibration, FFT Analyzer, Octave, Envelope, RMS, Excel, Matlab 7.1, Noise-Map.