Fast Hybrid Computation of the S-transform (ST) Through the Compact ST
摘要
Computation of the S-transform (ST) of a time series results in a 2-D complex time-frequency (t-f) representation that provides information about the local Fourier spectrum at every instant of time. The magnitude and phase spectra of the ST output provide quantitative and visual information about the local spectral content.The large computational and storage requirements of the ST place limitations on the usage of the ST. A recently developed compact S-transform (cST) points to an alternate method of computing the ST with significant economies in computation time and storage. With the cST, only a select fraction of the voices of ST are computed. Further significant economies are achieved through intra-voice decimation of the low frequency voices. The full ST matrix is then computed with interpolation. The resulting hybrid ST (hST) is in good agreement with the conventional direct computation of the ST. The improvements in computation speed and storage of the hST are more apparent with increase in the length of the time series.