The paper aims to determine the characteristic frequencies of an electric drill, by measuring and analyzing comparatively the variations of the acoustic intensity level, using the Fast Fourier Transform method (FFT). This was applied using a stand which had been specifically developed for the presented work. In two channel and multichannel systems, digital methods have been used for the calculation of cross properties as they were the only practical methods. Using digital techniques has gained considerable ground, being nowadays applied to problems once solved by resorting to analog methods. The increasing use of Fast Fourier Transform methods is found in single channel real time narrow band measurements and the Digital Filtering is replacing the Analog Filter bank which was used as the basis for real time analyzers operating with constant percentage bandwidth.
Single channel wireless EEG device for real-time fatigue level detection
