Publication Date:
2019-09-23
Description:
This study reports an adaptation of a parametric
echosounder system using 15 kHz as secondary frequency to
investigate the angular response of sub-bottom backscatter
strength of layered mud, providing a new method for enhanced
acoustic detection of buried targets. Adaptions to
achieve both vertical (0°) and non-vertical inclination (1–
15°, 30°, 45° and 60°) comprise mechanical tilting of the
acoustic transducer and electronic beam steering. Data were
acquired at 18 m water depth at a study site characterized by a
flat, muddy seafloor where a 0.1 m diameter power cable lies
1–2 m below the seafloor. Surveying the cable with vertical
incidence revealed that the buried cable can hardly be discriminated
against the backscatter strength of the layered mud.
However, the backscatter strength of layered mud decreases
strongly at 〉3±0.5° incidence and the layered mud echo pattern
vanishes beyond 5°. As a consequence, the backscatter
pattern of the buried cable is very pronounced in acoustic
images gathered at 15°, 30°, 45° and 60° incidence. The size
of the cable echo pattern increases linearly with incidence.
These effects are attributed to reflection loss from layered
mud at larger incidence and to the scattering of the 0.1 m
diameter buried cable. Data analyses support the visual impression of superior detection of the cable with an up to
2.6-fold increase of the signal-to-noise ratio at 40° incidence
compared to the vertical incidence case.
Type:
Article
,
PeerReviewed
Format:
text
