Digital Filtering for Circumferential Wave Separation

The excitation of a cylindrical structure by an acoustic wave gives rise to several circumferential waves. The received scattering signal is the result of different wave contributions. The analysis of this signal in time domain is difficult due to the superposition and overlapping of different wave contributions. In this chapter, we propose to use digital filtering in order to decompose the temporal signal into its components. This method is based on the isolation of the frequency content of each wave using the finite impulse response filter. The inverse Fourier transform of the isolated spectrum provides the contribution of the corresponding wave to the total temporal signal. Thereafter, the time–frequency representation is used as a tool for the verification of the isolated contribution. In addition, this representation can be used to identify the properties of the circumferential wave.