We heard of white noise and science even try to make an understanding of it. Here is a guy who goes into caves and do these filming as a hobby or maybe for a living and as he goes deeper and deeper, you can hear what sounds like voices in there. What does it sound to you? Some say that it is the sound of dead miners who is telling dude to "GET OUT" as it may be that of the hissing sound. You can hear it for yourself. Just bear with him as he walks you through this mine shaft. Pretty cool and dangerous if you have never gone into one before.
