This study reports an adaptation of a parametric\udechosounder system using 15 kHz as secondary frequency to\udinvestigate the angular response of sub-bottom backscatter\udstrength of layered mud, providing a new method for enhanced\udacoustic detection of buried targets. Adaptions to\udachieve both vertical (0°) and non-vertical inclination (1–\ud15°, 30°, 45° and 60°) comprise mechanical tilting of the\udacoustic transducer and electronic beam steering. Data were\udacquired at 18 m water depth at a study site characterized by a\udflat, muddy seafloor where a 0.1 m diameter power cable lies\ud1–2 m below the seafloor. Surveying the cable with vertical\udincidence revealed that the buried cable can hardly be discriminated\udagainst the backscatter strength of the layered mud.\udHowever, the backscatter strength of layered mud decreases\udstrongly at >3±0.5° incidence and the layered mud echo pattern\udvanishes beyond 5°. As a consequence, the backscatter\udpattern of the buried cable is very pronounced in acoustic\udimages gathered at 15°, 30°, 45° and 60° incidence. The size\udof the cable echo pattern increases linearly with incidence.\udThese effects are attributed to reflection loss from layered\udmud at larger incidence and to the scattering of the 0.1 m\uddiameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to\ud2.6-fold increase of the signal-to-noise ratio at 40° incidence\udcompared to the vertical incidence case.
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