| 摘要 |
<p>A marker to mark underwater objects characterised in that it undergoes whole body resonance when exposed to an incident acoustic wave. In one arrangement the marker comprises a shell (12) surrounding a water core. In other arrangements the marker is toroidal or cylindrical or tubular in shape. Holes (20) are provided in the shell to allow water freely to enter and leave the core when the marker is immersed in water. In the case of cylindrical or tubular shells, the cylinders or tubes can be open ended to allow water freely to flow into the interior of the shell. Best results are obtained when the marker is a sphere of aluminium, aluminium alloy or brass between 200mm and 400mm inclusive in diameter with a shell wall between 6mm and 15 mm inclusive thick, operating with an interrogating sonar or other acoustic transducer at 30 to 80KHz inclusive.</p> |
