I took this video this summer when i went on a trip to aomori. Osorezan is a mountain in the countryside, which is said to be the entrance to hell. The sound in the clip is boiling water under the ground. This is just speculation but because of the fact that you cant see the boiling water but only hear it, people believed it to be the entrance of hell. Otherwise, due to natural sulfur in the area, it stinks everywhere of rotten eggs. They built a temple around the area as a means to guard the entrance. I thought it was quite interesting.