Automatic Detection of Fixed Echoes in Sodar Facsimile Records Using the Wavelet Transform

Abstract

A method to detect and remove fixed echoes in sodar facsimile records is described. This method is based on the capability of the wavelet transform to objectively detect singularities in signals, and it is adapted to two-tone facsimile records. At the present time, no other relevant method for facsimile record processing, except human observation, has been described in the literature. Automatic removal of fixed echoes is useful during computer processing of facsimile records with modern algorithms in order to prevent false layer detection when it is not possible to avoid or remove fixed echoes before recording. A test of the method on complex examples shows its success and limitations.