Experimental acoustic signal analyzed by the parametric and non parametric time-frequency representations

In this paper, we introduce the parametric and non parametric time-frequency representations for modeling non-stationary signals particularly the acoustic signals. The impulse response backscattered by Aluminium cylindrical shell, of radii ratio equal to 0.95, is analyzed from these time-frequency representations. The first representation is called spectrogram distribution SP and the second is the time-varying autoregressive spectrum TVAS. In this work we have chosen these two representations for these interesting properties. The SP and TVARS are applied to identify the circumferential waves, propagating around the circumference of the tube, and to determine the cut-off frequency of these waves. From the time-frequency images obtained, we have determined the cut-off frequencies. These frequencies are compared with those computed by the proper modes theory given in the scientific literature. A good agreement is obtained.