The Hum

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 Hum on the Big Island of Hawaii, typically related to volcanic action, is heard in locations dozens of miles apart. The local Hawaiians also say the Hum is most often heard by men. 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 are hard to localize.

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".^[1]

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 hearers, but not by all of them. Many people hear the Hum only, or much more, inside buildings as compared with outdoors. Many also perceive vibrations that can be felt through the body. Earplugs are reported as not decreasing the Hum.^[2] The Hum is often perceived more intensely during the night.

In the Unsolved Mysteries segment called 'Mystery Hum', a tape re-creation of the Taos Hum was used for this segment. Robert Stack reported that one of the "Hum sufferers" created the audio tape, mainly for the purpose in that particular segment. This was done since their audio equipment didn't pick up low-frequency sounds very well, and so that the show's viewers and other non-"Hum sufferers" would get an idea of what the actual auditory phenomenon sounded like.

On 15 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.^[3][4] The captured hum's power spectral density peaks at a frequency of 56 hertz.^[5] In 2009, the head of audiology at Addenbrooke's Hospital in Cambridge, Dr. David Baguley managed to successfully record what he believes to be the hum with the help of acousticians at Salford University^[6]

History

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. However, in the 1970s and 1980s, a similar phenomenon had been the object of complaints from citizens, of media reports and of studies. 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.

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 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.^[7][8]

Some possible explanations

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

Tinnitus

Generated by the body, the auditory or the nervous system, with no external stimulus. However, the theory that the Hum is actually tinnitus fails to explain why the Hum can only be heard 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 fact that some people in the population perceive the Hum and others do not.

While hypothesized to be a form of low frequency tinnitus^[9] 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. Tinnitus is also generally worse in places with less exterior sound.

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.^[10]

Spontaneous otoacoustic emissions

Human ears generate their own noises, called spontaneous otoacoustic emissions, which about 30% of people hear. The people that 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.^[11]

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.^[12][13][14]

Media coverage

The Taos Hum was featured on the TV show Unsolved Mysteries,^[15] and it was also briefly mentioned in an episode of The X-Files.^[16]

See also

• Bloop
• Singing sand
• Slow Down

References

Further reading

• Deming, David (2004). "The Hum: An Anomalous Sound Heard Around the World". Journal of Scientific Exploration 18 (4): 571–595.  [1]
• Friedrich, Samantha M. Resident irritated by 'hum', The Thomaston Express, May 26, 2006. - Local Resident Experiencing the hum
• The Guardian staff. What's that noise?, The Guardian, October 18, 2001. - Article on the Largs Hum (Scotland) and the Hum in general.
• Pilkington, Mark. Humdinger, The Guardian, July 22, 2004. - General background.
• Tanimoto, Toshiro (2008). Geophysics: Humming a different tune. In: Nature 452 : 539. [2]
• National Public Radio USA. The Buzz behind Auckland's Hum

External links

• Taos Hum - Independent site by Bill Beaty concerning mostly the Hum in Taos, New Mexico.
• The Hum - Independent site by John Dawes, who claims the hum is an electrical interference effect with buildings.
• Summary by Joe Mullins of a study about the Taos Hum
• Mystery Hum Home Page - Site totally devoted to the Mystery Hum
• Have you heard 'the Hum'? - BBC article on The Hum.
• Wired - Scientists Track Down Source of Earth’s Hum (8/09)
• Anomalous Sounds at the Open Directory Project