Hum... The global... Hum?

The Earth gum is not tinnitus. So they say:
https://www.theguardian.com/cities/2019/mar/16/can-you-hear-the-mysterious-global-hum-apparently-many-of-you-do

Citando:
"He added: “While it must be stressed time and again that there are many sounds created by human activity that can sound like the Hum, and it takes some effort and knowledge to track those sounds down. They range from electrical noise, pumps, industrial machinery, and so on. Once we eliminate those sources, we are left with the worldwide phenomenon that I am studying.”"