Joint time-frequency analysis of electrochemical noise

Results have been presented for regular Fourier transformation of results o f electrochemical noise measurements. The variability of the frequency comp osition and the averaging character of the classical Fourier analysis have been shown for the example electrochemical noise records. Loss of informati on concerning the time evolution of the signal has been indicated. These in conveniences render difficult or even make impossible the drawing of conclu sions on the basis of a noise signal spectrum of non-stationary character. Two types of transformation have been presented belonging to the class of j oint time-frequency analysis methods. The first one, short-time Fourier tra nsformation (STFT) is based on application of a time window, determining th e localisation of the spectrum in the time domain. The second, (wavelet tra nsformation) is based on analysis of a signal on the basis of a family of f unctions formed through translation and scaling of an appropriately chosen localised mother function. Spectrograms obtained by the above methods have been presented, for electrochemical noise recordings. (C) 2001 Elsevier Sci ence B.V. All rights reserved.