The Hum – Wikipedia

Description

An essential feature of the humming phenomenon is the subjective perception of low -frequency tones or noises that are supposed to come from outside, but to which no acoustic cause can be assigned.[1] The humming sound is often described as a noise similar to a truck diesel engine running at idle in the distance, less frequently as a steady humming like that of a transformer station or a meter box, even more rarely as a rumbling, chugging or roaring in the ears or in the head. Repeatedly, those affected by hum have re-enacted their perception of hum with tone generators. This made it known that there is no uniform hum. Each affected person tuned into mostly 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 hum is heard by at least two percent of the population worldwide.[2][3][4] Perceptions of a hum are more common in silence and during nighttime hours. It is usually perceived to be louder indoors than outdoors. About half of those affected perceive it constantly, the other half only occasionally. The volume is experienced as fluctuating and the shape of the sound as sometimes erratic. The majority of those affected have the impression that a perceived hum creates beats with neighboring external tones and that it cannot be perceived for several days directly after traveling for several hours. Over a third of those affected report that the sound cuts off abruptly with certain head movements. Everyone affected feels an individual buzzing sound.[2] It is characteristic that those affected are initially convinced that someone/something from outside is invading their privacy in a massively disruptive, threatening and hurtful way, which they perceive as a restriction in their quality of life. They feel left alone because people close to them usually do not hear the same thing. Even ear doctors do not give any satisfactory advice, 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 tinnitus is already present and behaves completely differently from the perceived buzzing sound. In search of an external cause, the facilities within one’s own dwelling are first inspected. If these can be ruled out as the cause, those affected often search their surroundings for noise sources at night. Some of those affected feel like victims of a conspiracy. For many of those affected, the perceived sound loses importance after a few years or is no longer perceived as threatening. It becomes irrelevant or disappears entirely.

Story

The oldest and most common reports of hum come from the UK, where it was first widely reported in the national media in the 1950s.[1] In 1989, the buzzing phenomenon was first reported in the city of Taos, New Mexico, USA. From surveying 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 investigations concluded that environmental noise was not the cause of the Taos Hum, and that environmental electromagnetic sources were most likely not responsible either.[3] In Germany there were occasional mentions in the media between 2000 and 2002. The increased contact between those affected led to the foundation of the interest group for the clarification of the humming sound e. V. (IGZAB). She was contacted by 1500 affected people. A questionnaire specially designed for the observations of individuals affected was sent out and evaluated. The results are published.[2][4][5] After 200 victims filed a criminal complaint against unknown persons for bodily harm, the Baden-Württemberg Ministry of the Environment carried out measurements with special devices at 13 locations on May 2, 2001, for which no common cause could be found.[6] possible explanations Tinnitus and similarities with otoacoustic emissions Any sound that is perceived without an external acoustic cause is, by definition, tinnitus. According to this definition, the buzzing sound can be described as tinnitus. As early as 1940, Fowler distinguished between non-vibratory and vibratory tinnitus. Vibrational tinnitus is mechanical in origin and is heard like an external sound. Only vibratory tinnitus can beat with external sounds and does not cause permanent damage to the ear.[7] The majority of those affected by the hum observe beats between their hum and a neighboring external sound. If this is the case, the hum has two other properties significantly more frequently, namely that it only occurs after a delay of days when the person concerned returns from a trip, or that it disappears during certain head movements.[2] The hum has many properties such as spontaneous otoacoustic emissions (SOAEs). Both are observed to decrease in frequency over the years, they can be viewed as a van der pol system producing beats with adjacent external sounds, they can occur in local peaks with extremely improved hearing ability, they from about 2% of the population as tinnitus are audible that with a dose of about 2.4 g of aspirin they are eliminated after the first day and they disappear with certain head movements.[8]

Possible explanations Tinnitus and similarities with otoacoustic emissions

Any sound that is perceived without an external acoustic cause is, by definition, tinnitus. According to this definition, the buzzing sound can be described as tinnitus. As early as 1940, Fowler distinguished between non-vibratory and vibratory tinnitus. Vibrational tinnitus is mechanical in origin and is heard like an external sound. Only vibratory tinnitus can beat with external sounds and does not cause permanent damage to the ear.[7] The majority of those affected by the hum observe beats between their hum and a neighboring external sound. If this is the case, the hum has two other properties significantly more frequently, namely that it only occurs after a delay of days when the person concerned returns from a trip, or that it disappears during certain head movements.[2] The hum has many properties such as spontaneous otoacoustic emissions (SOAEs). Both are observed to decrease in frequency over the years, they can be viewed as a van der pol system producing beats with adjacent external sounds, they can occur in local peaks with extremely improved hearing ability, they from about 2% of the population as tinnitus are audible that with a dose of about 2.4 g of aspirin they are eliminated after the first day and they disappear with certain head movements.[8] It can be expected that the same structures and processes in the inner ear that are responsible for the occurrence of audible SOAEs are involved in the buzzing sound. The sensory organs responsible for the normal hearing process do not seem to be optimally tuned in a limited frequency range.[9] The buzzing sound, like audible SOAEs, can also be referred to as vibratory tinnitus. In both, the mechanical oscillations are within the auditory pathway. In contrast to SOAEs, the hum is currently not objectively measurable. The current classification of tinnitus into subjective and objective tinnitus is unsuitable for classifying the buzzing sound if it is caused by an illness and does not take into account mechanical vibrations, which are currently not objectively measurable. A special feature of the hum is its temporary disappearance after a change of location. It can be assumed that this phenomenon also occurs with SOAEs, but it is not known. Conceivable causes of this property can be an abrupt change in air pressure, gravity, prolonged exposure to vibrations or noise known to affect the inner ear. Other as yet unknown influences cannot be ruled out.

Electromagnetic fields

Electromagnetic fields emanating from digital mobile communications, DECT telephones or WLAN are not the cause of the buzzing sound, because it was already occurring before they appeared. In the vicinity of powerful pulsed high-frequency radiation or radar systems, some people experience auditory impressions which, however, do not resemble the nature of the hum, see Frey effect. However, other effects in this context cannot be ruled out due to some phenomena that are still unexplained.

Building vibrations caused by ground shaking

In principle, humming noises in buildings and living spaces can be caused by slight building vibrations.[11] The vibrations themselves can only be felt but not heard by humans. However, the secondary airborne noise emitted by vibrating walls is audible[12]. The spectrum of the audible secondary airborne noise corresponds to that of the vibrations of the walls. A sound spectrum in which low frequencies are disproportionately present or even a single low frequency stands out is perceived by people as unnatural and disturbing.[13] Environmental noises transmitted into living spaces pass through various physical low-pass filters on their way from the point of origin (point of emission) to the point of effect (point of immission).[13] One reason for this is that the attenuation of noise and vibration decreases as the frequency decreases. It is known that a vibration in the ground at half the frequency propagates twice as far before the sound level is attenuated to the same extent.[12] As a result, vibrations from originally purely low-frequency sources are transmitted largely without significant attenuation, or an originally broadband noise spectrum is colored low-frequency[13]. In addition, individual low-frequency parts of the spectrum can be further amplified by room and wall resonances.[14] Low-frequency sources of structure-borne noise are construction sites, as well as industrial or commercial facilities with rotating machines of high mass and high energy consumption, such as generators, motors or pumps.[15][16] Furthermore, wind turbines should be mentioned, which cause low-frequency ground vibrations via their foundations.[17] Another important source is road and rail transport. The secondary airborne noise, which is present in the event of a vibration load, can be analyzed on the basis of the TA Noise. The limit values ​​of the TA Noise are often complied with despite persistent complaints[13]. However, it is possible to analyze the situation using measurements on the basis of the vibration guideline[18]. 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 K B F T r {\displaystyle KB_{FTr}} {\displaystyle KB_{FTr}} can already be exceeded when no tactile perception of the actual vibration is perceptible.[19]

This text is based on the article WIKIPEDIA_Brummton phenomenon from the free encyclopedia Wikipedia and is licensed under a Creative Commons CC-BY-SA 3.0 Unported (abbreviated) license. A list of authors is available on Wikipedia.