7 - Transformée de Fourier discrète récursive avec fenêtre exponentielle dissymétrique

The spectrum of a non-stationary long lasting signal is got in a sliding window, in which a discrete Fourier transform (DFT) is realized. The calculation of that transform at each step is heavily time consumer, although a fast Fourier transform (FFT) algorithm is generally used . Furthermore, the spectral informations concern the full window . We propose the use of a non-symetrical exponential window, so that to localize the informations in the vicinity of the latent instant, and so that to save titre . The lost in frequency resolution is quite acceptable, and the recursive calculations are at least three tunes faster than with classical FFT.