https://www.nytimes.com/2018/02/19/world/canada/windsor-hum.html

The Windsor hum is back in the news! NYT reporting: “The University of Windsor report said the hum’s likely source was blast furnace operations on Zug Island on the Detroit River, which is densely packed with manufacturing. Activists complained that United States Steel, which operates the furnaces, has been uncooperative and secretive. A company spokeswoman did not respond to requests for comment.”

They also identify othwr places in the world with this low frequency hum like Taos.