The Hum is a phenomenon, or collection of phenomena, involving 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: e.g., the "Bristol Hum", the "Taos Hum", or the "Bondi Hum".
Data from a Taos Hum study suggests that a minimum of 2% and perhaps as many as 11% of the population could detect the Taos Hum and the Daily Telegraph in 1996 likewise reported a figure of 2% of people hearing the Bristol Hum. For those who can hear the Hum it can be a very disturbing phenomenon and it has been linked to at least 3 suicides in the UK. However, amongst those who cannot hear the hum and some specialists, there has been skepticism about whether it in fact exists.
The essential element that defines the Hum is what is perceived as a persistent low-frequency sound, often described as being comparable to that of a distant diesel engine idling, or to some similar low-pitched sound for which obvious sources (e.g., household appliances, traffic noise, etc.) have been ruled out. There are a number of audio reproductions of the Hum available on the web.
Other elements seem to be significantly associated with the Hum, being reported by an important proportion of hearers, but not by all of them. Some people hear the Hum only, or much more, inside buildings as compared with outdoors. Some perceive vibrations that can be felt through the body. Earplugs are reported as not decreasing the Hum.
On November 15, 2006, Dr. Tom Moir of the Massey University in Auckland, New Zealand made a recording of the Auckland Hum and has published it on the university's website. The captured Hum's power spectral density peaks at a frequency of 56 hertz. In 2009, the head of audiology at Addenbrooke's Hospital in Cambridge, Dr David Baguley, said that he believed people's problems with hum were based on the physical world about one-third of the time and the other two-thirds stemmed from people focusing too keenly on innocuous background sounds.
In Britain, the most famous example was the Bristol hum that made headlines in the late 1970s. It was during the 1990s that the Hum phenomenon began to be reported in North America and to be known to the American public, when a study by the University of New Mexico  and the complaints from many citizens living near the town of Taos, New Mexico, caught the attention of the media. The media took the story and disseminated the information.
This phenomenon has also been reported since 2010 throughout Windsor and Essex County in Ontario, Canada, where some residents claim it to be correlated with the time of day, or week, while others seem unaffected or unable to hear it. On April 20, 2012 the Canadian Government decided to officially investigate, and the launch of a study was announced on January 21, 2013. Current suspicions are that the noise originates on Zug Island.
The Hum has also been heard since at least 2004 by residents on Canada's southwest Coast in the region around the city of Vancouver.
The Hum has also frustrated residents in County Kerry, Ireland. This led to it being raised in the Irish Dáil, a house of government, by Michael Healy-Rae, who personally heard the Hum. The official response was described by Healy-Rae as "away with the fairies gobbledygook." The phenomenon was also recorded in 2012 in Seattle and Wellington, New Zealand.
The World Hum Database and Mapping Project was launched in December 2012, in order to build detailed mappings of hum locations and to provide a database of Hum-related data for professional and independent researchers.
Possible explanations 
Some explanations of hums for which no definitive source has been found have been put forth. These include:
A suggested diagnosis of tinnitus, a 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 the Hum can be heard only at certain geographical locations, to the degree those reports are accurate. There may exist individual differences as to the threshold of perception of acoustic or non-acoustic stimuli, or other normal individual variations that could contribute to the perception of the Hum by some people in the population and not by others.
While the Hum is hypothesized by some to be a form of low frequency tinnitus such as the venous hum, some sufferers claim 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.
People who both suffer from tinnitus and hear the Hum describe them as qualitatively different, and many hum sufferers can find locations where they do not hear the hum at all. An investigation by a team of scientists in Taos dismissed the possibility that the Hum was tinnitus as highly unlikely.[unreliable source?]
Spontaneous otoacoustic emissions 
Human ears generate their own noises, called spontaneous otoacoustic emissions, which about 30% of people hear. The people who hear these sounds typically hear a faint buzzing or ringing, especially if they are otherwise in complete silence, but most people don't notice them at all. However, these emissions occur with equal frequency across age groups within the population, and the Hum typically occurs in regional clusters, and rarely within large metropolitan areas.
Colliding ocean waves 
Researchers from the USArray Earthscope have tracked down a series of infrasonic humming noises produced by waves crashing together and thence into the ocean floor, off the North-West coast of the USA. Potentially, sound from these collisions could travel to many parts of the globe. No mechanism has been suggested to explain how the Hum is heard in the middle of remote land masses, hundreds of miles away from any ocean.
Mechanical devices 
In the case of Kokomo, Indiana, a city with heavy industries, the origin of the hum was thought to have been traced to two sources. The first was a pair of fans in a cooling tower at the local DaimlerChrysler casting plant emitting a 36 Hz tone. The second was an air compressor intake at the Haynes International plant emitting a 10 Hz tone. After those devices were corrected, however, the hum persisted.
Media coverage 
In popular culture 
See also 
- "Why is 'the hum' such a mystery?". British Broadcasting Company. Retrieved Jan 2013.
- "Complaints Surround the 'Kokomo Hum'". ABC. Retrieved Jan 2013.
- Melouney, Carmel (2009-05-24). "Bondi's mystery noise maker". The Daily Telegraph (News Ltd). Retrieved 2009-05-25.
- Deming, David (2004). "The Hum: An anomalous sound heard around the world". Journal of Scientific Exploration 18 (4): 571–594. Retrieved Jan 2013.
- Pilkington, Mark (July 22, 2004). "Humdinger". The Guardian.
- Alexander, James. "Have you heard 'the hum'?". BBC, 22nd May 2009. Retrieved Jan 2013.
- "The Buzz behind the Auckland Hum". NPR. November 22, 2006. Retrieved Jan 2013.
- Hanlon, Michael (20 May 2009). "Have you heard The Hum?". The Daily Mail. Retrieved Jan 2013.
- Moir, Tom (2006-11-15). "Auckland North Shore Hum". T.J.Moir Personal pages. University of Massey. Retrieved 2006-11-24.
- Hutcheon, Stephen (2006-11-17). "Mystery humming sound captured". Sydney Morning Herald (Fairfax). Retrieved 2006-11-24.
- Hutcheon, Stephen (2006-10-26). "Mystery noise is a real humdinger". Sydney Morning Herald (Fairfax). Retrieved 2006-11-24.
- Alexander, James (2009-05-19). "Have you heard 'the Hum'?". BBC News. Retrieved 2011-06-13.
- Mullins, Joe. "The Elusive Hum In Taos, New Mexico". University of New Mexico, 1995. Retrieved January 2013.
- Alleyne, Richard (2011-06-09). "Tiny village is latest victim of the 'The hum'". The Telegraph (London). Retrieved 2011-06-13.
- Battagello, Dave (August 5, 2011). "Rumblings may prompt lawsuit". The Windsor Star.
- Tweedie, Neil (June 18, 2011). "The Hum keeps people awake at night". The Daily Telegraph.
- "Taking Action on the 'Windsor Hum'". Canadian Consulate General, Foreign Affairs Media Relations Office. Retrieved 22 January 2013.
- "Ottawa investigates mysterious Windsor hum". CBC News. 2012-04-20.
- Deming, David (2004). "The Hum: An Anomalous Sound Heard Around the World". Journal of Scientific Exploration 18 (4): 573. Retrieved 2012-11-14.
- O'Mahony, John (1 March 2012). "‘The Hum’ leaves village ears ringing". Irish Examiner.
- O'Mahony, John (3 April 2012). "Locals despair as ‘The Hum’ makes life a living hell". Irish Examiner.
- O'Mahony, John (3 April 2012). "Locals despair as ‘The Hum’ makes life a living hell". Irish Examiner.
- "Mysterious hum in Seattle," ksdk.com. 6 September 2012. Retrieved 7 September 2012.
- "Wellington 'hum' becomes nationwide obsession," 3news, 11 October 2012. Retrieved 112 October 2012.
- "The World Hum Database and Mapping Project". Retrieved Jan 2013.
- Sheppard, L.; Sheppard, C. (1993). "The Phenomenon of Low Frequency Hums". Tinnitus. Norfolk Tinnitus Society. Retrieved 2011-06-13.
- The Taos Hum
- Abrams, M. An Inescapable Buzz. Discover Magazine. October 1995.
- Leggett, Hadley (August 7, 2009). "Scientists Track Down Source of Earth’s Hum". Wired. Retrieved 2011-06-13.
- Dacey, James (July 10, 2009). "Coasts confirmed as main source of Earth's 'hum'". physicsworld.com. Retrieved 2011-06-13.
- Walburn, Steve. "The Hearers" in Indianapolis Monthly, Dec. 2002.
- Cowan, James P. (October 2003). The Kokomo Hum Investigation (PDF) (615411). City of Kokomo Board of Public Works and Safety. Retrieved 2006-11-27.
- "Possible Source Found For Kokomo Hum: Hum Traced To Local Factory". TheIndyChannel.com (Internet Broadcasting Systems, Inc.). 2003-09-19. Retrieved 2006-11-27.
- "Taos hum", Unexplained events, Unsolved Mysteries
- "Top Ten Unexplained Phenomena", Strange news, Live Science
- "Drive". The X Files. Ten Thirteen Productions. November 15, 1998. Event occurs at 40:00.
Further reading 
- Friedrich, Samantha M. "Resident irritated by 'hum'", The Thomaston Express, May 26, 2006.
- The Guardian staff. "What's that noise?", The Guardian, October 18, 2001.
- NPR. "The Buzz behind Auckland's Hum". All Things Considered, November 22, 2006.
- Tanimoto, Toshiro (2008). "Geophysics: Humming a different tune". Nature 452: 539.