- Find Enemy: New advanced sonar systems, such as the SM2000 from Konigsberg Mesotech in Vancouver, Canada, distinguish among divers, large fish and submersibles. In this case, sonar picks up the intruder, tracks his path, and relays this information back to the ship.
- Test Water: After the threat is identified and the intruder´s path predicted, the sonic fence system kicks in. First, an acoustic projector tests the water conditions, sending a low-pressure signal to a hydrophone below the ship.
- Adjust Signal: After receiving the test signal, the hydrophone relays it to a "waveform" processor aboard the ship, which analyzes it to determine how water conditions such as salin-
ity or tem-perature modified the signal. The operator must account for these variables to ensure that the sound "peaks" in the right location.
- Blast Enemy: As the diver gets closer, the operator activates the system. The acoustic generator pumps out high-pressure sound waves, creating a sonic fence about 65 feet in diam-eter around the ship. Inaudible to humans, the frequency of the sound is tuned to produce nausea and even vomiting in humans