Studying noise measurement and analysis

This paper presents some aspects regarding to sound characteristics, how the sound pressure level can be expressed, and how the sound analysis can be used for fault detection. Sound level meter is used for sound measurement, which provides measurements of sound pressure levels and displays it in units of dB. The sound level meter and different types of used transducers are briefly presented. In industrial environment noise measurements are made because useful sound cannot be separated from other noises. Motors' working is followed by vibrations and oscillations which are in audible frequency domain so any changes of the environmental noise can lead to useful information. If a fault occurs, the produced vibration sound overlaps with the base sound signal and modulation appears. In case of different faults frequency and amplitude modulations appear. The latter can be easily detected due to the sideband frequencies in the frequency spectrum. Using Matlab functions, the Power Spectral Density of a signal can be obtained. Knowing the specific frequencies due to the rotating element and analyzing the PSD of measured noise faults can be localized. If sideband frequency around the fundamental frequencies is shown, then it has the meaning of an abnormality presence.