The Hum

The Hum is a name often given to widespread reports of a persistent and invasive low-frequency humming, rumbling, or droning noise not audible to all people. Hums have been reported in the United States, United Kingdom, New Zealand and Canada, and 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.
The Hum does not appear to be a single phenomenon. Different causes have been attributed, including local mechanical sources, often from industrial plants, as well as manifestations of tinnitus or other biological auditory effects.
Description.
A 1973 report mentions a university study of fifty cases of people complaining about a "low throbbing background noise" that others were unable to hear. The sound, always peaking between 30 and 40 Hz, was found to only be heard during cool weather with a light breeze, and often early in the morning. These noises were often confined to a wide area.
A study into the Taos Hum in the early 1990s indicated that at least two percent could hear it; each hearer at a different frequency between 32 Hz and 80 Hz, modulated from 0.5 to 2 Hz. Similar results have been found in an earlier British study. It seems to be possible for hearers to move away from it, with one hearer of the Taos Hum reporting its range was . There are approximately equal percentages of male and female hearers. Age does appear to be a factor, with middle aged people being more likely to hear it.
In 2006, Tom Moir, then of Massey University in Auckland, New Zealand, believed he has made several recordings of the Auckland Hum. His previous research using simulated sounds had indicated that the hum was around 56 hertz.
There is skepticism as to whether the hum exists as a physical sound. In 2009, the head of audiology at Addenbrooke's Hospital in Cambridge, David Baguley, said he believed people's problems with the hum were based on the physical world about one-third of the time, and stemmed from people focusing too keenly on innocuous background sounds the other two-thirds of the time. His research focuses on using psychology and relaxation techniques to minimise distress, which can lead to a quieting or even removal of the noise.
Geoff Leventhall, a noise and vibration expert, has suggested cognitive behavioral therapy may be effective in helping those affected. "It's a question of whether you tense up to the noise or are relaxed about it. The CBT was shown to work, by helping people to take a different attitude to it."
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.
In the case of Kokomo, Indiana, a city with heavy industry, the origin of the hum was thought to have been traced to two sources. The first was a 36-hertz tone from a cooling tower at the local DaimlerChrysler casting plant and the second was a 10-hertz tone from an air compressor intake at the Haynes International plant. After those devices were corrected, however, reports of the hum persisted.
Three hums have been linked to mechanical sources. The West Seattle Hum was traced to a vacuum pump used by CalPortland to offload cargo from ships. After CalPortland replaced the silencers on the machine, reports of the hum ceased. Likewise, the Wellington Hum is thought to have been due to the diesel generator on a visiting ship. A 35 Hz hum in Windsor, Ontario, is thought to have originated from a steelworks on the industrial zone of Zug Island near Detroit, with reports of the noise ceasing after the U.S. Steel plant there ceased operations in April 2020.
One hum in Myrtle Beach, South Carolina was suspected of originating at a Santee Cooper substation almost 2 miles away from the home of a couple who first reported it. The substation is home to the largest transformer in the state. One local couple sued the power company for the disruption the hum was causing them. The hum was louder inside their house than out, in part, they believed, because their house vibrated in resonance to the 60 Hz hum. The volume of the hum was measured at up to 64.1 dB in the couple's home.
Some sources claim that very low frequency radio waves or extremely low frequency radio waves that are used to communicate with submarines might be the source for the hum.
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.
While the Hum is hypothesized by some to be a form of low frequency tinnitus such as the venous hum, some report it is not internal, being worse inside their homes than outside. However, others insist that it is equally bad indoors and outdoors. Some people notice the Hum only at home, while others hear it everywhere they go. Some sufferers report that it is made worse by soundproofing (e.g., double glazing), which serves only to decrease other environmental noise, thus making the Hum more apparent.
Spontaneous otoacoustic emissions.
Human ears generate their own noises, called spontaneous otoacoustic emissions (SOAE). Various studies have shown 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 hissing (cicada insect like sound), buzzing or ringing, especially if they are otherwise in complete silence.
Researchers who looked at the Taos Hum considered otoacoustic emissions as a possibility.
Jet stream.
Philip Dickinson suggested at an Institute of Biology conference in 1973 that the 30 to 40 Hz hum could be a result of the jet stream shearing against slower-moving air and possibly being amplified by power line posts, some of which were shown to vibrate, or by rooms which had a corresponding resonant frequency. Geoff Leventhall of the Chelsea College Acoustics Group dismissed this suggestion as "absolute nonsense".
Animals.
One of the many 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.
Media coverage.
The Taos Hum was featured on the TV show "Unsolved Mysteries". It was also featured in "LiveScience"'s "Top Ten Unexplained Phenomena", where it took tenth place.
BBC Radio 4 in the UK featured an investigation of the Hum phenomena in their "Punt PI" fact-based comedy programme.
Hums have recently been reported in both Frankfurt & Darmstadt, Germany.