Dimensional characterization of an elastic tube using the spectrogram and the reassigned spectrogram time-frequency analysis

The dimensional characterization of an elastic tube can be done thanks to its cut-off frequencies of the waves propagating around the tube. In this work, we propose to determine certain geometrical properties of a tube such as the radii radio b/a. The spectrogram and the reassigned spectrogram time-frequency representation of a signal are used in this work to access to the sought parameters. These techniques are applied to the acoustic signals backscattered by a copper tube immersed in water. The time-frequency images of this signal permit to determine the cut-off frequency of the anti-symmetric wave A1. From these frequencies we have determined with precision the radii radio b/a of the tube.