Multi-frequency analysis of seabed echoes using wavelet transform

The methods based on analysis of boftom backscatter data from a single-beam echosounder have achieved special attention in the seabed identification problem. due to their simplicity over ofher more sophisticated acoustic techniques like side scan sonar or multibeam surveys. The majority of these methods analyses the scattering phenomena mostly in time domain (echo envelope). However, the frequency echo components carry concurrent information, which can be also used in boftom characterisation. The paper proposes the time-frequency approach to the boftom characterisation and presents the application of Wigner- Ville Distribution and wavelet transform of boftom backscatter data. The examples of continuous and discrete wavelet transforms of actual echo envelopes received at three boftom types for three different operating frequencies (38, 120 and 420 kHz) are shown. Their characteristic features are compared and parameters for classification schemes are proposed. The results of classification procedure are good with comparison with those of ofher simple acoustic methods.