The S transform is variable window of short time Fourier transform (STFT) or an

extension of wavelet transform (WT). It is based on a scalable localizing Gaussian

window and supplies the frequency dependent resolution. In this tutorial, we

introduce the fundamental function of S transform and the generalized S transform.

Furthermore, we present some applications of S transform: seismogram analysis,

analysis of engine induction noise in acceleration, and power quality analysis. Then

compare the result of S transform with other time-frequency analysis and exhibit some

different windows of S transform.