All evidence points to it being a hoax. There are numerous known methods being used to produce these, the simplest being the addition of sounds to existing video. When the mono/stereo patterns of the sounds do not match that of the original video, it's pretty obviously a fake. Some of the sounds have been matched to movies such as war of the worlds. There is also the fact that these started out as isolated and and simple incidents and evolved into something more complicated and sinister, which is exactly what we expect to see in hoax phenomena.
But it is a very spooky concept. Reminds me of a horror movie I saw recently, Yellow Brick Road, which was also a very creepy concept with a disappointing reveal.