| 摘要 |
<p>The invention provides a system for detecting the presence of living creatures other than fish in bodies of liquid, the system including: transmitting means positioned within the body of liquid for transmitting acoustic energy through the body of liquid; receiving means positioned within the body of liquid for receiving reflected acoustic energy; wherein at least part of the reflected acoustic energy received by said receiving means is compared with at least one reflected acoustic energy reference and an alarm activation signal is created if at least part of said reflected acoustic energy corresponds at least partially to at least one living creature reflected acoustic energy reference. The living creature reflected acoustic energy reference is preferably the reflected acoustic energy expected to be received by said receiving means if a living creature was present in said body of liquid. Preferably, said living creature reflected acoustic energy reference is characterised by a central region of little or no acoustic energy, corresponding to the air inside the living creature. Preferably, the acoustic energy includes an acoustic wave and more preferably is at least one supersonic acoustic wave.</p> |
