a weak sonar signal
While the animals lack sonar , they do posses superb directional underwater hearing and the ability to see in near-darkness.
And evidence that sonar kills whales goes way beyond coincidence.
the fishing nets are detectable by dolphin sonar
Out in the Atlantic, vast Japanese factory ships work nonstop, using modern sonar detection to spot the tuna shoals they sweep the ocean clean of fish.
Hearing the unusual ping, the animals might turn on their echolocators - their sonar - and then they can sense the net.
Now, video footage and sonar data proves conclusively that the wreck is not Centaur.
For instance, he said, its active and passive sonar systems are aging, thus shortening the range of its monitoring.
The SUNS system can determine positions underwater by the use of small buoys which broadcast the position and time references by sonar signals.
The animal's sensitive sonar is capable of picking up information about the shape of distant objects, and it was trained to respond in some distinctive way to this piece of information.