Acoustic detection and classification of fluid-filled cylinders embedded in sediments

An open-water trial was carried out using a parametric sonar system with the aim of detecting and classifying embedded or partially embedded objects such as pipelines, lost cargo and mines. This was a contribution to the European Commission´s MAST-III DEO (Detection of Embedded Objects) project. The trial involved the detection of back-scattered signals from a water-filled, thin-walled steel cylinder with flat end-caps. Comparisons of incident and back-scattered signals were made at both the ´primary´ frequency of 75 kHz and at ´secondary´ frequencies in the range 1-13 kHz for sine wave, chirp and Ricker pulses. The main finding was that both specular reflections and resonance effects could be observed and it is proposed that these could contribute to the classification of targets.