Taos Hum!

The Hum is a phenomenon, or collection of phenomena, involving widespread reports of a persistent and invasive low-frequency humming, rumbling, or droning noise not audible to all people. Hums have been widely reported by national media in the UK and the United States. The Hum is sometimes prefixed with the name of a locality where the problem has been particularly publicized.

In 1997 Congress directed scientists and observers from some of the most prestigious research institutes in the nation to look into a strange low frequency noise heard by residents in and around the small town of Taos, New Mexico. For years those who had heard the noise, often described by them as a “hum”, had been looking for answers. To this day no one knows the cause of the hum.

Possible Explanations :

Mechanical devices

Although an obvious candidate, given the common description of the hum as sounding like a diesel engine, the majority of reported hums have not been traced to a specific mechanical source.

Tinnitus

A suggested diagnosis of tinnitus, a self-reported disturbance of the auditory system, is used by some physicians in response to complaints about the Hum. Tinnitus is generated internally by the auditory and nervous systems, with no external stimulus. However, the theory that the Hum is actually tinnitus fails to explain why some hearers report that the Hum can be heard only at certain geographical locations.

Spontaneous otoacoustic emissions

Human ears generate their own noises, called spontaneous otoacoustic emissions (SOAE). Various studies have showed that 38–60% of adults with normal hearing have them, although the majority are unaware of these sounds. The people who do hear these sounds typically hear a faint buzzing or ringing, especially if they are otherwise in complete silence.

Researchers who looked at the Taos Hum considered otoacoustic emissions as a possibility, and eventually concluded that this was likely the case.

Fish

One of the possible causes of the West Seattle Hum considered was that it was related to the midshipman fish, also known as a toadfish. A previous hum in Sausalito, California, also on the west coast of the United States, was determined to be the mating call of the male midshipman. However, in that case the hum was resonating through houseboat hulls and affecting the people living on those boats. In the West Seattle case, the University of Washington researcher determined that it would be impossible for any resonating hum, transmitted via tanker or boat hulls, to be transmitted very far inland; certainly not far enough to account for the reports.

The Scottish Association for Marine Science hypothesised that the nocturnal humming sound heard in Hythe, Hampshire in the UK could be produced by a similar "sonic" fish.The council believed this to be unlikely because such fish are not commonly found in inshore waters of the UK. As of February 2014 the source had not been located, although the sound has now been recorded.