Location of Repository

Studies into the detection of buried objects (particularly optical fibres) in saturated sediment. Part 2: design and commissioning of test tank

By T.G. Leighton and R.C.P. Evans


This report is the second in a series of five, designed to investigate the detection of<br/>targets buried in saturated sediment, primarily through acoustical or acoustics-related<br/>methods. Although steel targets are included for comparison, the major interest is in<br/>targets (polyethylene cylinders and optical fibres) which have a poor acoustic<br/>impedance mismatch with the host sediment. This particular report details the<br/>construction of a laboratory-scale test facility. This consisted of three main<br/>components. Budget constraints were an over-riding consideration in the design.<br/>First, there is the design and production of a tank containing saturated sediment. It<br/>was the intention that the physical and acoustical properties of the laboratory system<br/>should be similar to those found in a real seafloor environment. Particular<br/>consideration is given to those features of the test system which might affect the<br/>acoustic performance, such as reverberation, the presence of gas bubbles in the<br/>sediment, or a suspension of particles above it. Sound speed and attenuation were<br/>identified as being critical parameters, requiring particular attention. Hence, these<br/>were investigated separately for each component of the acoustic path.<br/>Second, there is the design and production of a transducer system. It was the intention<br/>that this would be suitable for an investigation into the non-invasive acoustic<br/>detection of buried objects. A focused reflector is considered to be the most costeffective<br/>way of achieving a high acoustic power and narrow beamwidth. A<br/>comparison of different reflector sizes suggested that a larger aperture would result in<br/>less spherical aberration, thus producing a more uniform sound field. Diffraction<br/>effects are reduced by specifying a tolerance of much less than an acoustic<br/>wavelength over the reflector surface. The free-field performance of the transducers<br/>was found to be in agreement with the model prediction. Several parameters have<br/>been determined in this report that pertain to the acoustical characteristics of the water<br/>and sediment in the laboratory tank in the 10 – 100 kHz frequency range.<br/>Third, there is the design and production of an automated control system was<br/>developed to simplify the data acquisition process. This was, primarily, a motordriven<br/>position control system which allowed the transducers to be accurately<br/>positioned in the two-dimensional plane above the sediment. Thus, it was possible for<br/>the combined signal generation, data acquisition and position control process to be coordinated<br/>from a central computer.<br/>This series of reports is written in support of the article “The detection by sonar of<br/>x<br/>difficult targets (including centimetre-scale plastic objects and optical fibres) buried<br/>in saturated sediment” by T G Leighton and R C P Evans, written for a Special Issue<br/>of Applied Acoustics which contains articles on the topic of the detection of objects<br/>buried in marine sediment. Further support material can be found at<br/>http://www.isvr.soton.ac.uk/FDAG/uaua/target_in_sand.HTM

Topics: GC, QC, TC
Publisher: University of Southampton
Year: 2007
OAI identifier: oai:eprints.soton.ac.uk:46559
Provided by: e-Prints Soton

Suggested articles



  1. (1980). A comparison of the AIUM/NEMA, IEC and FDA
  2. (1988). A E, “An examination of the spherical scatterer approximation in aqueous suspensions of sand”,
  3. (1995). A model for acoustic backscatter from muddy sediments”,
  4. (1987). A S, “A new shallow-ocean technique for determining the critical angle of the seabed from the vertical directionality of the ambient noise in the water column”,
  5. (1994). Acoustic imaging using ambient noise: Some theory and simulation results”,
  6. (1999). Acoustic penetration of the seabed, with particular application to the detection of non-metallic buried cables”, PhD Thesis,
  7. (1987). Acoustic Properties of Sediments”, Acoustics and Ocean Bottom, edited by
  8. (1977). Acoustical Oceanography; Principles and Applications,
  9. (1981). Acoustics: An Introduction to Its Physical Principles and Applications,
  10. (1998). An experimental investigation of acoustic penetration into sandy sediments at sub-critical grazing angles”,
  11. (1992). Analysis of Echoes from a Solid Elastic Sphere in Water”,
  12. (1945). Attenuation of sound in marine sediments”,
  13. (1992). Backscattering by a suspension of spheres”,
  14. (1998). Characteristion of Propagation Parameters for High Frequency Sonar in Turbid Coastal Waters”,
  15. (1940). Composition of sea water”,
  16. (1972). Compressional-wave attenuation in marine sediments”,
  17. (1998). Depth-pressure relationships in the oceans and seas”,
  18. (1982). Descriptive Physical Oceanography: An Introduction,
  19. (1969). Development of Simple Equations for Accurate and More Realistic Calculation of the Speed of Sound in Sea Water”,
  20. (1971). Elastic Properties of Marine Sediments”,
  21. (1995). Electronic beam steering of shock waves”,
  22. (1950). Experiments on acoustic absorption in sand and soil”,
  23. Fundamentals of Acoustics, 3rd Edition,
  24. (1998). Fundamentals of underwater acoustics”
  25. (1992). Glegg S A L, “Acoustic daylight: Imaging the ocean with ambient noise”,
  26. (1990). Handbook, 2nd Edition,
  27. (1998). Heathershaw A D, “Measurement at 50 - 150 kHz of Absorption due to Suspended Particulate Matter”,
  28. (1966). Hydrodynamics and Heat Transfer in Fluidised Beds, The M.I.T.
  29. (1998). Nonlinear acoustic scattering from a gassy poroelastic seabed”,
  30. Observations of acoustic backscattering by elastic cubes”,
  31. (1987). Optics, 2nd Edition,
  32. (1983). Principles of Underwater Sound,
  33. (1993). Selective focusing in multiple-target media: The transfer matrix method”,
  34. (1991). Sonar Signal Processing,
  35. (1977). Sound absorption in sea water”,
  36. (1976). Sound attenuation as a function of depth in the sea floor”,
  37. (1977). Sound scattering from a fluid sphere revisited”,
  38. (1997). Sounds impossible”,
  39. (1988). Stochastic Modeling of Seafloor Morphology: Inversion of Sea Beam Data for Second-Order Statistics”,
  40. (1997). Survey, International Underwater Systems Design,
  41. (1992). Technical Documentation for Hydrophone Types
  42. (1948). The Absorption of Sound in Suspensions of Irregular Particles”,
  43. (1994). The Acoustic Bubble,
  44. (1998). The Detection of Cylindrical Objects of Low Acoustic Contrast Buried in the Seabed”,
  45. (1996). The effect of suspended particulate matter on sound attenuation in seawater”,
  46. (1998). The effect of temperature, pressure, and salinity on sound attenuation in turbid seawater”,
  47. (1991). The iterative time reversal mirror: A solution to self-focusing in the pulse echo mode”,
  48. (1995). The Physics of Vibrations and Waves, 4th Edition,
  49. (1945). The Theory of Sound,
  50. (1991). Theory of Wave Scattering from Random Rough Surfaces, Adam Hilger,
  51. (1980). Waves in Layered Media, 2nd Edition,

To submit an update or takedown request for this paper, please submit an Update/Correction/Removal Request.