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Low frequency noise 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. It has been widely reported by national media in the UK and the United States. Colloquially, this may be referred to as, for example, the "Bristol Hum" or the "Taos Hum".

Data from a Taos study suggests that around two percent of the population could detect the sound. For those who report hearing it, low frequency noise can be a very disturbing phenomenon, but there is skepticism about whether it exists as a physical phenomenon.

Description

The essential element that defines low frequency noise 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.

For those who claim to hear it, this can be a very disturbing phenomenon and it has been linked to at least three suicides in the UK.

A study into the "Taos Hum" 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 48 km. 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.

There is skepticism about whether low frequency noise genuinely exists. In 2009, the head of audiology at Addenbrooke's Hospital in Cambridge, David Baguley, said he believed people's problems with low frequency noise 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 current research focuses on using psychology and relaxation techniques to minimise the distress, which leads to a quieting or even removal of the noise. Leventhall, who prepared a report for the UK government on the subject, similarly suggested that cognitive behavioural therapy was effective: "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."

History

There has been little mainstream attention. Only a handful of articles have been published in scientific literature, including: Leventhall, 2004, 2003; Mullins & Kelly, 1998, 1995; Broner, 1978; Vasudevan & Gordon, 1977. Others publications include: Wilson, 1979; Hanlon, 1973.

Possible explanations

See also: infrasound

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 noise reports 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.

Two 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 third hum in Windsor is likely to have originated from a steelworks on the industrial zone of Zug Island.

Spontaneous otoacoustic emissions

Human ears generate their own noises, called spontaneous otoacoustic emissions, which affect between 38 percent to 60 percent of people, although the majority are unaware of these sounds. The people who 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.

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.

In popular culture

In a 1998 episode of The X-Files titled "Drive", Agent Mulder speculates that extremely low frequency (ELF) radio waves "may be behind the so-called Taos Hum".

See also

• List of unexplained sounds

References

1. "Humdinger". The Guardian. 22 July 2004.
2. ^ "The mystery of the Taos hum" (PDF). Acoustical Society of America. Autumn 1995.
3. ^ "Mystery of people who hear the hum". New Scientist. 13 December 1979. pp. 868–870.
4. "Hmmmmmmmmmmmm...?". People. 21 September 1992.
5. "The Phenomenon of Low Frequency Hums". Norfolk Tinnitus Society. 1993.
6. ^ "A Review of Published Research on Low Frequency Noise and its Effects" (PDF). Defra. May 2003.
7. "Have you heard 'the Hum'?". BBC News. 19 May 2009.
8. "Who, What, Why: Why is 'the hum' such a mystery?". BBC News. 13 June 2011.
9. Leventhall, H. G. (2004). "Low frequency noise and annoyance". Noise & Health. 6 (23): 59–72.
10. Broner, N. (1978). "The effects of low frequency noise on people—A review". Journal of Sound and Vibration. 58: 483–500. doi:10.1016/0022-460x(78)90354-1.
11. Vasudevan, R. N.; Gordon, C. G. (1997). "Experimental study of annoyance due to low frequency environmental noise". Applied Acoustics. 10 (1): 57–69.
12. "Can some people hear the jet stream?". New Scientist. 8 November 1973. pp. 415–416.
13. "Expert says hum is not a sound". Kokomo Tribune. 3 June 2004. pp. 1&12.
14. "Expert says hum is not a sound". Hum Forum. 3 June 2004.
15. "'The Hum' followup: CalPortland installs second silencer, hopes that's the fix". West Seattle Blog. 7 December 2012.
16. "Wellington hum disappears". 3 News. 16 October 2012.
17. "Singapore's frigate 'Stalwart' source of Wellington hum?". 3 News. 11 October 2012.
18. "Report: Windsor Hum Likely From Zug Island "Blast Furnace Operations"". windsoriteDOTca. 23 May 2014.
19. Tinnitus: A Multidisciplinary Approach. 2013. p. 32. ISBN 1-86156-403-1. {{cite book}}: |work= ignored (help)
20. Abrams, M. (October 1995). "An Inescapable Buzz". Discover Magazine. p. 20. {{cite web}}: Missing or empty |url= (help)
21. "In Taos, Researchers Can Hum It, but They Can't Name That Sound". LA Times. 1 September 1993.
22. "Taoseños' Ears Still Humming". Albuquerque Journal. 9 December 2007.
23. "Seattle 'Hum' May Be Due To Midshipman Fish That Produce Sound For Mating". The Huffington Post. 7 September 2012.
24. "Humming Toadfish Are the Buzz of Sausalito". NBC. 16 June 1986.
25. "West Seattle's now-famous 'Hum': Apparently NOT a fish's fault". West Seattle Blog. 11 September 2012.
26. "Mystery hum keeping people awake may be love-making fish". The Daily Telegraph. 23 October 2013.
27. "Southampton Water mystery droning prompts more moaning". BBC News. 24 October 2013.
28. "Minutes of a meeting of the New Forest Environmental Protection Liaison Committee" (PDF). New Forest District Council. 7 February 2014. p. 4.
29. "Unsolved Mysteries: Ghosts (2005)". Amazon.com. Disc 4, "Mystery Hum".
30. "Spooky! The Top 10 Unexplained Phenomena". LiveScience. 10 January 2007.
31. "In A Tiny English Town, A 'Hum' Pierces Each Night". NPR. 15 June 2011.
32. "Drive". Ten Thirteen Productions. The X Files. November 15, 1998. Event occurs at 40:00.

Further reading

• "What's that noise?". The Guardian. October 18, 2001.
• Moorhouse, Andy; Waddington, David; Adams, Mags (February 2005). "Procedure for the assessment of low frequency noise complaints" (PDF). Acoustics Research Centre, University of Salford.
• Leventhall, Geoff. "Coping Strategies". Defra.

• especially "Development of a course in computerised Cognitive Behavioural Therapy" (PDF). 2009.
• and "Coping Strategies for Low Frequency Noise" (PDF). 2008.

External links

• Low Frequency Noise FAQ, University of Salford

• Unidentified sounds
• Noise
• Noise pollution
• New Mexico culture
• Fringe science