The sonic barrier is a series of evenly-spaced pylons that surround the barracks encampment. The barrier itself is not actually the pylons, but a continuous stream of high-intensity waves that are generated by the pylons. The range of the waves, as seen in "Par Avion", reaches only between the ground and the top of the pylons. Tending to be lethal, the waves can cause severe cerebral hemorrhaging to humans who pass through them. Although humans can successfully breach the barrier before they "die," it is apparent in "Left Behind" that the monster cannot pass between the pylons.
The sonic barrier was found by the search party of Kate, Locke, Sayid and Rousseau on their mission to rescue Jack. According to Mikhail Bakunin, their prisoner, and DHARMA cabling map discovered by Sayid in the Flame, the fence extends all the way around the area containing the Barracks, acting as a security measure to either keep individuals in/out.
A keypad is used to enable the sonic barrier
Locke seemingly killed Mikhail Bakunin by pushing him into the barrier, however, Mikhail did not die and was seen helping the parachutist.("D.O.C.")
After he seemingly perished Locke, Kate, Sayid and Rousseau made a ramp of a tree trunk in order to scale the barrier and bypass it. In doing so, they did not break the connection between each barrier pylon, which Sayid guessed was the trigger for the sonic waves.
The barrier can be deactivated. In Left Behind, Kate and Juliet encounter the fence while running from the Monster. Juliet says that the fence is not active. Juliet and Kate cross to the other side, then Juliet enters the code 1623 into a data pad, lifts a panel, turns a knob, and the fence is reactivated. The Monster rushes to Juliet and Kate, but the fence repels it. The Monster cannot break through, and goes away. Juliet explains, "we don't know what it is but we know it doesn't like our fences." ("Left Behind")
Trivia
Spectral analysis of the sound produced by the sonic barrier
- According to spectral analysis of the sound made by the sonic barrier, one of the frequency bands corresponds to 972 Hz, which is the average resonant frequency of the human skull.
- On the Blast door map, there a notation near the top which mentions a security barrier.
The Sonic barrier from season 1
- On some parts from season 1, the fence can be seen from far away. ("The Other 48 Days")
Unanswered Questions
| Unanswered questions |
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- For fan theories about these unanswered questions, see: Sonar fence/Theories
- Is there a way to deactivate the fences from outside the perimeter?
- Was the barrier originally built to protect against The Monster, or for some other reason?
- Is the Fence actually lethal?
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