The “Taos Hum” in New Mexico, USA, is a mysterious sound described as that of a truck engine running in the distance by those who can hear it. It has never been definitively recorded; however, “hearers” (around 2% of residents) sometimes even claim associated nausea and headaches. This phenomenon is now being reported around the world and is particularly prevalent in the USA and Western Europe. Possible explanations include a very low-frequency natural vibration of the earth, distant machinery, and conspiracy theories of secret government activity. (http://bit.ly/2HsbnKP, http://bit.ly/2kQGhng)