|The Sonic Barrier|
|Name||The Sonic Barrier|
|Introduced In||Par Avion|
The Sonic Barrier surrounds the Barracks and blocks any attempt to pass through them. If an individual makes an attempt to enter through the field a sonic wave is emitted which results in the individual suffering a cerebral hemorrhage.
The first discovery of the sonic barrier was made by Locke, Sayid, Kate, Danielle, and Mikhail as they were making their way to the Barracks after following a map showing cabling running across the island which was found inside The Flame Station. According to Mikhail, the sonic barrier encircles the entire barracks, and the map supports his claim.
In an effort to test whether or not the barrier was still in operation, Locke grabs Mikhail and forces him into the field between the pylons, which results in Mikhail's apparent death. The four then devise a plan to head over the pylons evading the sonic field, doing so, they chop down a tree trunk and use it to climb above.In "Left Behind", while being chased by the monster, Juliet leads Kate to another section of the Sonic Barrier. She assures Kate that the fence is turned off, then enters a code in a keypad on the outward-facing side of one of the pillars. The keypad then pulls away to reveal a power button. Once Kate is on the correct side of the barrier, Juliet reactivates the fence. The monster then catches up with them and slams into the barrier. Unable to pass through, the monster retreats back into the jungle, and Juliet explains that, while the Others do not know what the monster is, they do know that it dislikes their fences. In LaFleur, Richard Alpert also makes an apparent reference to this fact when he tells Horrace Goodspeed that the fence may keep other things away but not the others. It may be argued that the fence was setup by the Dharma Initiative most likely to protect themselves from the monster, as the fences have a limited height and can be climbed over it unharmed. Further, it is also seen in all episodes that the monster only travels in thick pile along the ground only and apparaently this limited height was sufficient enough to keep the monster from crossing.