| 摘要 |
The novel method substantially reduces the pressure pulse, generated by a first radial motion of a body of water, by changing the radial motion into axial motion. The change from radial motion into axial motion is produced by generating a second radial motion of opposite phase within the body of water. The method can be used to substantially reduce the pressure pulse, generated by the implosion of a body of water, by generating an explosion in the body of water. It can also substantially reduce the pressure pulse generated by an explosion within a body of water, by generating an implosion of the body of water. The method can further by used to generate within a body of water an impulsive acoustic signal by sequentially generating within the body of water a first explosion and a second explosion. The apparatus (10) comprises a signal chamber (14) which contains a first charge (Va) of gas (G1). A normally-closed valve (12) maintains the signal chamber (14) closed and has a discharge port (16) into the water. A second chamber (14 min ) contains a second charge (Vb) of compressed gas (G2). A second fast-acting valve (12 min ) normally maintains the second chamber (14 min ) closed and has an outlet (16 min ) into the water. A controller (20, 20 min ) explosively opens the first valve (12) so as to generate an impulsive acoustic signal (P0) and a first bubble (1). The controller subsequently opens the second valve (12 min ) to thereby release the second charge (Vb) from the second chamber (14 min ) into the water, while the first bubble (1) is near its maximum volume. |
