Technology – What is the SonarBell?
  • The SonarBell works through the constructive interference
    of sound waves when they meet after transiting the shell
    and core

  • It is totally passive and omnidirectional

  • Maximum target strength varies from -5 dB to -30 dB
    across the frequency range of 4 kHz to 1200 kHz*

  • Specific frequencies and target strengths are achieved
    by changing the thickness of the shell and other properties

  • The range depends on SonarBell size and frequency of
    the sonar

               * For a 200 mm sphere
Typical return from a  SonarBell
  • Distinguishing between different SonarBells acoustically,
    is made easier by changing the overall diameter of the

  • The acoustic diameter can be found by measuring the
    time difference between the front and back echo.  

  • The acoustic diameter is larger than the balls physical
    diameter due to the speed of sound in the core being
    slower than the speed of sound in water
2 Shell types
  • Engineered plastic >100kHz
             Lubricated high performance polyamide
             PPA Resin
             No COSH concerns
             High pressure >400T moulding

  • Aluminium <100kHz
             Careful selection of billet
             Turned from billet
             Identical construction
             Final operation are flood holes
SonarBell has two reflections
           A .  Front Echo (lover level)
           B.  Focussed return (high level)
Shell manufacture
Core manufacture
  • 3D printed molds

  • Silicon based product

  • Room cure, platinum catalyst
             COSH issues before set
             Harmless once set

  • Sized to leave 1.5mm annulus
             Allows water to flood the Bell
             No pressure on shell
             Tight coupling shell to core
             Pressure tested to 4100m

  • All cores RFID tagged
SonarBell™ - stanchions
Attachments / ancillaries