The Taos Hum is a mysterious low-frequency sound that has been reported in the small town of Taos, New Mexico since the early 1990s. The sound is described as a persistent, low-pitched hum that is heard by some people in the area, while others do not
From Wikipedia
The Hum is a persistent and invasive low-frequency humming, rumbling, or droning noise audible to many, but not all, people in an area. Hums have been reported in many countries, including Australia, Canada, the United Kingdom, and the United States. They are sometimes named according to the locality where the problem has been particularly publicized, such as the "Taos Hum" in New Mexico and the "Windsor Hum" in Ontario.