If Juliet really did camouflage herself and Kate from Smokie/Cerberus/The Monster by intentionally tripping into the mud, could that be why we got our first impressions of the Others as barefoot, dirty savages in the jungle? Do they travel that way when outside of Otherville because it's harder for Smokie to see them?
I think the Fence is an Electromagnetic Fence......not a Microwave, not a sonic fence. The "Sonic" hum could just be the electricity powering up the magnetic coils or whatever is in the posts. Dharma was experimenting with Electromagnetism after all. Smokie is probably a mechanical/robotic/nanotech construct machine......as such would be suceptible to Electromagnetism. So I would guess that once Smokie reached the Electromagnetic Fence, he got repelled.......which is why it looks like he hit a stone wall instead of getting zapped.
It almost looked like Smokie was confused after he hit the fence, he kind of spread out sideways slowly.....and then took off. Why didn't he go over the fence? Maybe Smokie couldn't see past the Electromagnetic Fence when it activated......so he's chasing Julliet and Kate by whatever vision he's got, he gets too close to the fence and the electromagnetics turn on.......Smokie slams into the fence. Smokie's thinking "WTF?" for a sec. and he doesn't see Kate & Juliett anymore due to the Fence is on, he lets out a pissed off yelp and takes off. I would figure if he could see Kate & Juliett, and the fence "hurt" him. He would stay on the otherside of the fence and start smacking the fence at other spots to see if he can get through, instead of giving up so easily. Remeber what Smokie did at the plane with the Piliot? Couldn't get to the pilot inside the plane, so he shut up and stayed outside quietly waiting. Pilot sticks his head out, Smokie gets him! Smokie could probably see the piliot, just couldn't get to him until he stuck his head out. I think people can get through the fence if they're quick, I've watch Patchy die a bunch of times......looks like he deliberately stopped in the middle of the fence & turned around after he was shoved. Maybe Patchy is a cyborg with with some electronics in his head behind his eye patch, LOL.
You might have something with the Camoflague. Maybe Smokie is programed to kill anything that is Cilvilized such as humans. So Smokie has to figure out what is Human, and what is animal.....otherwise Smokie will be going around killing all the animals on the island, and since Smokie was probably made by those Hippy Dharma guys back in the 70's, killing animals or their animal experiements is a no no. So how does Smokie figure out what is human and what is animal? Perhaps getting muddied up in the dirt & mud will fool Smokie into thinking Juliett & Kate are just some filify apes. Perhaps the Others dress up like dirty savages outside of Otherville so Smokie would think they're Animals and not try to kill them. That would also explain why the Others are always sneaking around in the Jungle dressed as savages......animals don't roam around the forest like Military Commandos.....which the Others can easiy do if they wanted to.....since it looks like a portion of them are Ex-Military or Law Enforcement. It would make sense that the Others weren't ever dirty savages because how the heck would a bunch of dirty savages with spears & rocks defeat the Dharma Scientist who had guns. (Dharma had Dharma guns......Desmond's Pistol he was going to shoot himself with said Dharma on it). This would also explain why the Others had their fake "Savage" camp by the cliffs when they were fooling Michael into thinking they're Savages. Maybe it wasn't so much to make Michael think they were Savages, but they were also scared that Smokie would come get them. Everytime the Others are outside of Otherville, they look like Savages.