The time courses recorded provided information on the phenomenon in question,
however, in order to extract it, application of the appropriate mathematical method proved
necessary. The results obtained belong to a group of non-stationary signals the analysis of
which forces one to apply time-frequency methods. Simultaneous extraction of information
concerning the time-frequency structure of a signal being analysed is possible owing to a
Short Time Fourier Transform (STFT). Because of its simplicity mathematical and physical
interpretation it is very common used tool. The main weakness of STFT is constant timefrequency
resolution which effect on analysis precision for different object dynamics. So it is