I have heard 'the hum'. In my house in western Connecticut, at night when nothing else is on, everything is quiet. I'm far from the ocean. There is no industry near by. No trucks. Nothing. There is a hum... maybe about 40 - 70Hz. It's creepy the first time you hear it. It seemed to be coming from the ground, and the walls. I moved to the bedroom it was there too. It's very quiet. You can't hear it if anything else is on.

If you say this to people they think you are crazy. I've had my ears checked for other reasons and they are fine. I'm not on any medications, or anything like that. The hum is not ocean wave vibration forces. The hum is constant and consistent. It sounds of mechanical precision. I have little doubt the sound is from a man made object.

From Wikipedia: "The Hum" History

There has been little mainstream attention. Only a handful of articles have been published in scientific literature, including: Leventhall, 2004,[15] 2003;[8] Cowan, 2003;[16] Mullins & Kelly, 1998, 1995;[4] Broner, 1978;[17] Vasudevan & Gordon, 1977.[18] Others publications include: Frosch, 2013,[19] Deming, 2004;[20] Fox, 1989;[21] Wilson, 1979;[5] Hanlon, 1973.[22]

The Hum has been repo rted worldwide.[12] The World Hum Database and Mapping Project was launched in December 2012, in order to build detailed mappings of hum locations and to provide a database of Hum-related data for professional and independent researchers.[23]

http://en.wikipedia.org/wiki/The_Hum