Humming sound phenomenon

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The humming sound phenomenon ( English The Hum or Taos Hum ) refers to the repeated perception of low-frequency tones or noises reported from many areas of the world by individuals with an initially unrecognizable cause.

description

An essential feature of the hum phenomenon is the subjective perception of low-frequency tones or noises that supposedly come from outside, but which cannot be assigned an acoustic cause. The humming tone is often described as a noise similar to a truck diesel engine running at idle in the distance, less often as a steady hum like that of a transformer station or a meter box, even less often than a rumbling, chugging or roaring in the ears or in the head. People affected by humming sounds have repeatedly simulated their hum perceptions with tone generators. This made it known that there is no uniform hum. Each affected person usually set several different individual frequencies between approx. 30 and 80 Hz, which were monaurally or binaurally modulated with approx. 0.5 Hz to 2 Hz . The humming sound is heard by at least two percent of the population worldwide.

Perceptions of a humming sound occur more frequently in silence and during the night. It is usually perceived louder in closed rooms than outdoors. About half of those affected notice it all the time, the other half only temporarily. The volume is experienced as fluctuating and the shape of the tone as sometimes erratic. The majority of those affected have the impression that a perceived humming tone creates beats with neighboring external tones and that it cannot be perceived for several days immediately after traveling for several hours. Over a third of those affected report that the sound stops suddenly when they move certain head movements. Everyone affected feels an individual humming sound.

It is characteristic that those affected are initially convinced that someone / something is intruding into their privacy from the outside in a massively disruptive, threatening and hurtful way, which they perceive as a restriction of the quality of life. You feel left alone because people close to you usually do not hear anything. Ear specialists do not give satisfactory advice either, as they determine that almost all of those affected have a healthy ear with normal or above-average hearing. The diagnosis of tinnitus is often vehemently rejected by those affected, especially if a tinnitus is already present that behaves completely differently than the perceived humming sound. In search of an external cause, the facilities inside the home are first inspected. If these can be excluded as the cause, those affected often search their surroundings for sources of noise even at night. Some people feel like victims of a conspiracy.

For many of those affected, the perceived tone loses its meaning after a few years or is no longer perceived as threatening. It becomes irrelevant or disappears entirely.

history

The oldest and most frequent reports of hums come from Great Britain, where it was first widely reported in the national media in the 1950s.

In 1989 in the city of Taos , New Mexico , USA, the hum sound phenomenon was first reported. From a survey of residents of Taos and the surrounding area, Mullins and Kelly calculated that at least 2% of residents heard a hum. During this time they scientifically investigated the phenomenon on behalf of the government with considerable effort. The research found that environmental noise was not the cause of the Taos Hum and that electromagnetic sources in the environment were most likely not responsible either.

In Germany there were occasional mentions in the media between 2000 and 2002. The increased contact of those affected led to the establishment of the interest group for the clarification of the humming sound e. V. ( IGZAB ). She was contacted by 1,500 victims. A questionnaire specially designed for the observations of individual victims was sent and evaluated. The results have been published.

After a criminal complaint by 200 victims against unknown persons for bodily harm, the Baden-Württemberg Ministry of the Environment began measuring with special devices at 13 locations on May 2, 2001, and no common cause could be found.

Possible explanations

Tinnitus and Similarities to Otoacoustic Emissions

Any sound that is perceived without an external acoustic cause is by definition tinnitus . According to this definition, the humming sound can be described as tinnitus. As early as 1940 Fowler distinguished between non-vibratory and vibratory tinnitus. Vibratory tinnitus is mechanical in origin and is heard like an external sound. Only vibratory tinnitus can vibrate with external sounds and does not cause permanent damage to the ear.

The majority of those affected by a humming sound observe beats between their humming sound and an adjacent external sound. If this is the case, the humming sound has two other properties significantly more often, namely that it only occurs again with a delay of days when the person concerned returns from a trip, or that it disappears during certain head movements.

The humming tone has many properties such as spontaneous otoacoustic emissions (SOAEs). Both are observed to have their frequencies lower over the years, they can be viewed as a van der Pol system that creates beats with neighboring external tones that they can occur in local peaks with extremely improved hearing ability Approx. 2% of the population can be heard as tinnitus, that with a dose of approx. 2.4 g of aspirin it can be eliminated after the first day and that it disappears with certain head movements.

It is to be expected that the same structures and processes in the inner ear are involved that are responsible for the occurrence of audible SOAEs. Sense organs responsible for the normal hearing process do not seem to be optimally tuned in a limited frequency range.

The humming sound, like audible SOAEs, can be described as vibratory tinnitus. In both cases, the mechanical oscillations are within the auditory pathway. In contrast to SOAEs, the humming sound is currently not objectively measurable. Today's common division of tinnitus into subjective and objective tinnitus is unsuitable for classifying the humming sound if it is based on a disease and does not take into account mechanical vibrations, which are currently not objectively measurable.

A special property of the humming sound is its temporary disappearance after a change of location. Whether this phenomenon will also occur in SOAEs can be assumed, but not known. Possible causes for this property could be an abrupt change in air pressure , the force of gravity , prolonged exposure to vibration or noise that are known to affect the inner ear. Other as yet unknown influences cannot be ruled out.

Extremely good hearing locally

Often there is locally extremely improved hearing in the area of ​​the humming sound. Under these conditions, ambient noises can produce the audible impression of the humming sound or amplify an existing humming sound. In these cases, the hum is actually generated or amplified by external sounds.

electromagnetic fields

Electromagnetic fields emanating from digital cellular networks, DECT telephones or WLAN are not the cause of the humming sound because it occurred before they appeared. In the vicinity of powerful, pulsed high-frequency beams or radar systems, some people have hearing impressions that, however, do not resemble the nature of the humming sound, see Frey effect . However, other effects in this context cannot be ruled out because of some as yet unexplained phenomena.

Building vibrations caused by ground shaking

In principle, humming noises in buildings and living spaces can be caused by slight building vibrations. The vibrations themselves can only be felt by humans, but not heard. What is audible, however, is the secondary airborne sound, which is emitted by vibrating walls. The spectrum of the audible secondary airborne sound corresponds to that of the vibrations of the walls. A sound spectrum in which low frequencies are strongly disproportionately present or even a single low frequency is perceived as unnatural and annoying by humans.

Environmental noises transmitted into living spaces pass through various physical low-pass filters on their way from the place of their origin (place of emission) to the place of their effect (place of immission). One reason for this is the decrease in the attenuation of noises and vibrations as the frequency decreases. It is known that a vibration in the ground at half the frequency spreads about twice as far before an equally strong attenuation of the sound level occurs. As a result, vibrations from originally purely low-frequency sources are transmitted largely without significant attenuation or an originally broadband noise spectrum is colored at low frequencies. In addition, individual low-frequency components of the spectrum can be further amplified by room and wall resonances.

Low-frequency structure-borne noise sources are construction sites, as well as industrial or commercial facilities with rotating machines of high mass and with high energy consumption, such as generators, motors or pumps. Wind power plants should also be mentioned, which cause low-frequency ground vibrations through their foundations. Another important source is road and rail transport.

The secondary airborne noise present in the event of a vibration exposure can be analyzed on the basis of the TA Lärm . Often the limit values ​​of the TA Lärm are met despite persistent complaints. However, it is possible to analyze the situation by measurement based on the vibration guideline. The limit values ​​of the DIN 4150-2 standard used here are defined in such a way that they also take the secondary effects into account from the outset. For example, the assessment vibration strength can already be exceeded when no tactile perception of the actual vibration is perceptible.

literature

Web links

Footnotes

  1. ↑ a b D. Deming: The hum: An anomalous sound heard around the world. In: Journal of Scientific Exploration. 18, 2004, pp. 571-595.
  2. ↑ a b c d F. Frosch: New findings on the humming sound. In: Tinnitus Forum, magazine of the German Tinnitus League e. V. ( DTL ) 4, 2008, pp. 42-43.
  3. ^ A b J. H. Mullins, JP Kelly: The mystery of the Taos hum. ( Memento of the original from August 16, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: Echoes. 5, 1995, pp. 1-6. @1@ 2Template: Webachiv / IABot / acousticalsociety.org
  4. ^ A b F. G. Frosch: Manifestations of a low-frequency sound of unknown origin perceived worldwide, also known as “The Hum” or the “Taos Hum”. In: International Tinnitus Journal. 20, 2016, pp. 59-63.
  5. ^ FG Frosch: Possible joint involvement of the cochlea and semicircular canals in the perception of low-frequency tinnitus, also called “The Hum” or “Taos Hum”. In: International Tinnitus Journal. 21, 2017, pp. 62-66.
  6. ↑ Thomas Delekat: The great hum. In: welt.de . May 12, 2001, accessed January 2, 2015 .
  7. ↑ EP Fowler: Head noises: Significance, measurement and importance in diagnosis and treatment. In: Archives of Otolaryngology , 32, 1940, pp. 903-914.
  8. ^ FG Frosch: Hum and otoacoustic emissions may arise out of the same mechanisms. In: Journal of Scientific Exploration. 27, 2013, pp. 603-624.
  9. ^ MJ Penner: Audible and annoying spontaneous otoacoustic emissions. A case study. In: Archives of otolaryngology. Volume 114, Number 2, February 1988, pp. 150-153, ISSN  0886-4470 . PMID 3337771 .
  10. ^ S. Wilson: Mystery of people who hear the hum. In: New Scientist , Dec. 13. 1979, 84, pp. 868-870. limited preview in Google Book search
  11. ↑ Secondary emitted structure-borne noise. (PDF) Swiss Society for Acoustics, October 13, 2018, accessed on October 13, 2018 .
  12. ↑ a b M. Heckl, HA Müller: Taschenbuch der Technischen Akustik . Springer, 1995.
  13. ↑ a b c d Joachim Feldmann, André Jakob: Low-frequency residential noise - causes, effects and reduction options . In: DAGA'06 Braunschweig . 2006.
  14. ↑ Harvey H. Hubbard: Noise Induced House Vibrations and Human Perception . In: Noise Control Engineering Journal . 1982.
  15. ↑ Birgitta Berglund, Peter Hassmén, RF Soames Job: Sources and effects of low-frequency noise . In: The Journal of the Acoustical Society of America . 1996.
  16. ↑ Mark R. Svinkin: Soil and Structure Vibrations from Construction and Industrial Sources . In: Sixth International Conference on Case Histories in Geotechnical Engineering . 2008.
  17. ↑ Rachel Westwood: Seismic monitoring and multiphysics modeling of ground-borne vibrations from small wind turbines 2012.
  18. ^ State Office for Nature, Environment and Consumer Protection North Rhine-Westphalia: Effects on people and buildings. Retrieved October 6, 2018 .
  19. ↑ Federal / State Working Group on Immission Control (LAI): Shock guideline. Retrieved October 6, 2018 .