The Hum

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The Hum is a generic name for a series of phenomena involving a persistent and invasive low-frequency humming noise not audible to all people. Hums have been reported in various geographical locations. In some cases a source has been located. A well known case was reported in Taos, New Mexico, and thus The Hum is sometimes called the Taos Hum: the unsolved nature of the hum in Taos has become part of the appeal of Taos. Hums have been reported all over the world, especially in Europe. The Hum is most often described as sounding somewhat like a distant idling diesel engine. Typically "The Hum" is difficult to detect with microphones, and its source and nature is a mystery to the listener.

The "Hum" is sometimes prefixed with the name of a locality where the problem has been particularly publicized: e.g., the "Bristol Hum" or the "Taos Hum".

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[edit] Description

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.

Other elements seem to be significantly associated with the Hum, being reported by an important proportion of Hum sufferers, but not by all of them. Many people hear the Hum only, or much more, inside buildings as compared with outdoors. Many Hum sufferers can also perceive vibrations that can be felt through the body. Earplugs are reported as not decreasing the Hum. The Hum is often perceived more intensely during the night.

Some people perceive the Hum continuously, but others perceive it only during certain periods. For some people, the perceived Hum can represent a faint sound and a mild annoyance, while for others who perceive the Hum's sound and/or vibrations more intensely it represents a nuisance that can seriously interfere with daily activities. Common consequences include a lack of sleep, as the Hum can keep some sufferers awake or wake them in the middle of the night.

On 15th November 2006 Dr Tom Moir, of the University of Massey in Auckland, New Zealand, made a recording of the Auckland Hum and has published it on the university's website[1][2]. The captured hum's power spectral density peaks at a frequency of 56 Hertz[3].

[edit] History

It is 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. However, in the 1970s and 1980's, a similar phenomenon had been the object of complaints from citizens, of media reports and of studies, mostly in the United Kingdom but also in other countries such as New Zealand.[4] It is difficult to tell if the Hum reported in those earlier cases and the Hum that began to be increasingly reported in North America in the 1990s should be considered identical or of different natures. During the last decade, the Hum phenomenon has been reported in many other cities and regions in North America and Europe and in some other regions of the world.

[edit] Explanations

In the case of Kokomo, Indiana, a city with heavy industries, the source 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 Daimler Chrysler casting plant emitting a 36 Hz tone. The second was an air compressor intake at the Hayes International plant emitting a 10Hz tone.[5][6]

[edit] Some possible explanations

Some explanations of hums, for which no definitive source has been found, have been put forth. These include:-

[edit] Man-made noises

High frequency attenuation of distant industrial sounds or stereo subwoofers from homes, cars, and music venues. As sound moves through the atmosphere or ground, the high frequencies decrease in amplitude more rapidly than the low frequency ones, which subsequently travel greater distances. The low-frequency sounds can be amplified by walls and structural geometry, and sound like ambiguous rumblings or hums. Industrial machinery such as compressors, pumps and fans can also produce similar types of sounds. Although this is one of the explanations that first come to mind, ordinary microphones have failed to detect the Hum and investigations have failed to convincingly trace the Hum to such sources[citation needed]. Studies in the UK have addressed this issue.

[edit] Infrasound made by geological events

Infrasound from different possible sources, possibly geologic or plate tectonic in nature.

[edit] Pulsed microwaves

A phenomenon similar to the microwave auditory effect from pulsed microwave sources, possibly in combination with other factors. The thermoelastic mechanism may or may not be involved. Various types of electromagnetic sources could involve different physical or physiological mechanisms or a combination thereof. Some of the components of the electromagnetic environment, and examples of their possible combined effects, have been discussed in the annex to the report about the Hum by the experts hired by the city of Kokomo, Indiana.

[edit] Electromagnetic caused by meteors

A variant of the audio frequency electromagnetic emissions generated upon the entry of a meteor and its disintegration in the upper atmosphere. The disintegration of larger meteors in the upper atmosphere is known to release megawatts of power in the audio frequency range, primarily through the interaction of the resulting ionization trail with the Earth's magnetic field. See, for example Listening to Leonids for a description of the meteor audio effect. (It is also speculated that the "solar wind" may be causing a similar effect to the "meteor audio effect.")

[edit] Extremely Low Frequency communications systems

Communication systems, such as submarine communications systems that use extremely low frequency (ELF) radio transmissions. Proponents of this theory suggest the transmissions may somehow produce effects either directly or indirectly through mechanisms similar or different of those by which higher frequencies are detected.

[edit] Ionospheric heating systems

Large-scale effects of one or several of the ionospheric heating projects in Norway, the U.S. or Russia, such as HAARP in Gakona, Alaska.

[edit] Tinnitus

Generated by the body, the auditory or the nervous system, with no external stimulus. Somewhat like tinnitus, but at lower frequencies. However, this theory fails to explain why the Hum can only be heard at certain geographical locations, or indoors as opposed to outdoors. There exists no such thing as an "indoor tinnitus". On the other hand, 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 fact that some people in the population perceive the Hum and others do not.

While hypothesized to be a form of low frequency tinnitus[1] 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. More mystery is added as some only notice the hum at home, while others hear it everywhere they go. Some reports indicate that it is made worse by attempted soundproofing (e.g., double glazing), which only serves to decrease other environmental noise, thus making the Hum more apparent.

[edit] The tensor tympani muscle making the eardrum tremble

As of 2005, a scientific hypothesis suggests the Hum originates on the eardrums of affected individuals by the tensor tympani muscle trembling. (The tensor tympani is a muscle within the inner ear for tightening the eardrum.) The 40-page hypothesis can be read in German on the pages of the German Association for Research about the Hum, IGZAB (InteressenGemeinschaft Zur Aufklärung des Brummtonphänomens). See: http://www.IGZAB.de . See de:Brummton-Phänomen.

[edit] Multiple

Any combination of two or more of the above types of explanations.

[edit] Trivia

  • The Taos Hum was featured on the TV show Unsolved Mysteries.
  • The Taos Hum was also mentioned, specifically the submarine radio theory, on the sixth season episode of The X-Files, "Drive."

[edit] See also

[edit] References

  1. ^ Moir, Tom (2006-11-15). Auckland North Shore Hum. T.J.Moir Personal pages. University of Massey. Retrieved on 2006-11-24.
  2. ^ Hutcheon, Stephen. "Mystery humming sound captured", Sydney Morning Herald, Fairfax, 2006-11-17. Retrieved on 2006-11-24.
  3. ^ Hutcheon, Stephen. "Mystery noise is a real humdinger", Sydney Morning Herald, Fairfax, 2006-10-26. Retrieved on 2006-11-24.
  4. ^ Researchers investigating things that go hum in the night. Massey University (October 11, 2006). Retrieved on 2006-10-19.
  5. ^ Cowan, James P. (October 2003). "The Kokomo Hum Investigation" Acentech Incorporated (Acentech Project No. 615411). Retrieved on 2006-11-27. 
  6. ^ "Possible Source Found For Kokomo Hum: Hum Traced To Local Factory", TheIndyChannel.com, Internet Broadcasting Systems, Inc., 2003-09-19. Retrieved on 2006-11-27.

[edit] External links

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