- Noise health effects
Noise health effects are the
healthconsequences of elevated sound levels. Elevated workplace or other noisecan cause hearing impairment, hypertension, ischemic heart disease, annoyance, sleep disturbance, and decreased school performance. Changes in the immune systemand birth defects have been attributed to noise exposure, but evidence is limited.cite journal |author=Passchier-Vermeer W, Passchier WF |title=Noise exposure and public health |journal=Environ. Health Perspect. |volume=108 Suppl 1 |issue= |pages=123–31 |year=2000 |pmid=10698728 |doi=] Although some presbycusismay occur naturally with age,cite journal |author=Rosenhall U, Pedersen K, Svanborg A |title=Presbycusis and noise-induced hearing loss |journal=Ear Hear |volume=11 |issue=4 |pages=257–63 |year=1990 |pmid=2210099 |doi=] in many developed nations the cumulative impact of noise is sufficient to impair the hearing of a large fraction of the population over the course of a lifetime.cite news | url = http://www.cbsnews.com/stories/2007/02/18/ap/health/mainD8NC00AO0.shtml | last = Schmid | first = RE | title=Aging nation faces growing hearing loss | publisher= CBS News| date = 2007-02-18 | accessdate=2007-02-18] [Senate Public Works Committee, " Noise Pollution and Abatement Actof 1972", S. Rep. No. 1160, 92nd Cong. 2nd session] Noise exposure has also been known to induce tinnitus, hypertension, vasoconstrictionand other cardiovascularimpacts. [cite web | url = http://ist-socrates.berkeley.edu/~lohp/graphics/pdf/hw24en08.pdf | title = Noise: Health Effects and Controls | publisher = University of California, Berkeley| accessdate = 2007-12-22 ] Beyond these effects, elevated noise levels can create stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors.cite book |author=Kryter, Karl D. |title=The handbook of hearing and the effects of noise: physiology, psychology, and public health |publisher=Academic Press |location=Boston |year=1994 |pages= |isbn=0-12-427455-2 |oclc= |doi=] The most significant causes are vehicle and aircraft noise, prolonged exposure to loud music, and industrial noise.
The mechanism of
hearing lossarises from trauma to stereociliaof the cochlea, the principal fluid filled structure of the inner ear.Fact|date=December 2007 The pinna combined with the middle earamplifies sound pressure levels by a factor of twenty, so that extremely high sound pressure levels arrive in the cochlea, even from moderate atmospheric sound stimuli. Underlying pathology to the cochleaare reactive oxygen species, which play a significant role in noise-induced necrosisand apoptosisof the stereocilia.cite journal |author=Henderson D, Bielefeld EC, Harris KC, Hu BH |title=The role of oxidative stress in noise-induced hearing loss |journal=Ear Hear |volume=27 |issue=1 |pages=1–19 |year=2006 |pmid=16446561 |doi=10.1097/01.aud.0000191942.36672.f3] Exposure to high levels of noise have differing effects within a given population, and the involvement of reactive oxygen species suggests possible avenues to treat or prevent damage to hearing and related cellular structures.
The elevated sound levels cause trauma to the
cochlear structure in the inner ear, which gives rise to irreversible hearing loss.S. Rosen and P. Olin, "Hearing Loss and Coronary Heart Disease", Archives of Otolaryngology, 82:236 (1965)] A very loud sound in a particular frequency range can damage the cochlea's hair cells that respond to that range thereby reducing the ear's ability to hear those frequencies in the future. [ [http://www.headwize.com/articles/hearing_art.htm HeadWize - Article: Preventing Hearing Damage When Listening With Headphones (A HeadWize Headphone Guide) ] ] However, loud noise in "any" frequency range has deleterious effects across the entire range of human hearing. [ [http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA056415 High-Frequency Hearing Loss Incurred by Exposure to Low-Frequency Noise ] ] The outer ear (visible portion of the human ear) combined with the middle earamplifies soundlevels by a factor of 20 when sound reaches the inner ear. ["Noise: A Health Problem" United States Environmental Protection Agency, Office of Noise Abatement and Control, Washington, DC 20460, August, 1978]
Hearing loss is somewhat inevitable with age. Though older males exposed to significant
occupational noisedemonstrate significantly reduced hearing sensitivity than their non-exposed peers, differences in hearing sensitivity decrease with time and the two groups are indistinguishable by age 79.cite journal |author=Rosenhall U, Pedersen K, Svanborg A |title=Presbycusis and noise-induced hearing loss |journal=Ear Hear |volume=11 |issue=4 |pages=257–63 |year=1990 |pmid=2210099 |doi=] Women exposed to occupational noise do not differ from their peers in hearing sensitivity, though they do hear better than their non-exposed male counterparts. Due to loud music and a generally noisy environment, young people in the United States have a rate of impaired hearing 2.5 times greater than their parents and grandparents, with an estimated 50 million individuals with impaired hearing estimated in 2050.cite web | url=http://www.cbsnews.com/stories/2007/02/18/ap/health/mainD8NC00AO0.shtml | last = Schmid | first = RE | title=Aging nation faces growing hearing loss | publisher= CBS News| date = 2007-02-18 | accessdate=2007-02-18]
In Rosen's work on
health effects and hearing loss, one of his findings derived from tracking Maaban tribesmen, who were insignificantly exposed to transportation or industrial noise. This population was systematically compared by cohortgroup to a typical U.S. population. The findings proved that aging is an almost insignificant cause of hearing loss, which instead is associated with chronic exposure to moderately high levels of environmental noise.
Noise has been associated with important cardiovascular health problems.cite journal |author=Ising H, Babisch W, Kruppa B |title=Noise-Induced Endocrine Effects and Cardiovascular Risk |journal=Noise Health |volume=1 |issue=4 | pages = 37–48 | year = 1999 | pmid = 12689488 |doi=| url = http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=1999;volume=1;issue=4;spage=37;epage=48;aulast=Ising] In 1999, the World Health Organization concluded that the available evidence showed suggested a weak association between long-term noise exposure above 67-70 dB(A) and hypertension. [cite web | last = Berglund | first = B | coauthors = Lindvall T, Schwela D, Goh KT | year = 1999 | publisher =
World Health Organization| title = World Health Organization: Guidelines for Community Noise | url = http://www.who.int/docstore/peh/noise/guidelines2.html] More recent studies have suggested that noise levels of 50 dB(A) at night may also increase the risk of myocardial infarctionby chronically elevating cortisolproduction.cite journal |author=Maschke C |title=Stress Hormone Changes in Persons exposed to Simulated Night Noise |journal=Noise Health |volume=5 |issue=17 | pages = 35–45 | year = 2003 | pmid = 12537833 | doi = |url = http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2002;volume=5;issue=17;spage=35;epage=45;aulast=Maschke | accessdate = 2007-12-22] cite journal |author=Franssen EA, van Wiechen CM, Nagelkerke NJ, Lebret E |title=Aircraft noise around a large international airport and its impact on general health and medication use |journal=Occup Environ Med |volume=61 |issue=5 |pages=405–13 |year=2004 |pmid=15090660 |doi=] cite journal |author=Lercher P, Hörtnagl J, Kofler WW |title=Work noise annoyance and blood pressure: combined effects with stressful working conditions |journal=Int Arch Occup Environ Health |volume=65 |issue=1 |pages=23–8 |year=1993 |pmid=8354571 |doi=]
Fairly typical roadway noise levels are sufficient to constrict arterial blood flow and lead to elevated blood pressure; in this case, it appears that a certain fraction of the population is more susceptible to vasoconstriction. This may result because annoyance from the sound causes elevated
adrenalinelevels trigger a narrowing of the blood vessels ( vasoconstriction), or independently through medical stress reactions. Other effects of high noise levels are increased frequency of headaches, fatigue, stomach ulcers and vertigo. ["Noise: A Health Problem" United States Environmental Protection Agency, Office of Noise Abatement and Control, Washington, DC 20460, August, 1978]
U.S. Environmental Protection Agencyauthored a pamphlet in 1978 that suggested a correlation between low-birthweight babies (using the World Health Organizationdefinition of less than 2,500 g (~5.5 lb) and high sound levels, and also correlations in abnormally high rates of birth defects, where expectant mothers are exposed to elevated sound levels, such as typical airportenvirons. Specific birth abnormalities included harelip, cleft palate, and defects in the spine. According to Lester W. Sontag of The Fels Research Institute(as presented in the same EPA study): “There is ample evidence that environment has a role in shaping the physique, behavior and function of animals, including man, from conception and not merely from birth. The fetusis capable of perceiving sounds and responding to them by motor activity and cardiac rate change." Noise exposure is deemed to be particularly pernicious when it occurs between 15 and 60 days after conception, when major internal organs and the central nervous systemare formed. Later developmental effects occur as vasoconstriction in the mother reduces blood flow and hence oxygenand nutrition to the fetus. Low birth weights and noise were also associated with lower levels of certain hormones in the mother, these hormones being thought to affect fetal growth and to be a good indicator of proteinproduction. The difference between the hormone levels of pregnant mothers in noisy versus quiet areas increased as birth approached.
Because some stressful effects depend on qualities of the sound other than its absolute decibel value, the annoyance associated with sound may need to be considered in regard to health effects. For example, noise from airports is typically perceived as more bothersome than noise from traffic of equal volume. [Miedema and Oudshoorn 2001 cited in cite web|url=http://www.medscape.com/viewarticle/516462|title=Hypertension and exposure to noise near airports|publisher=Medscape] Annoyance effects of noise are minimally affected by demographics, but fear of the noise source and sensitivity to noise both strongly affect the 'annoyance' of a noise. [cite journal | author = Miedema HME, Vos H | title = Demographic and attitudinal factors that modify annoyance from transportation noise | journal = Journal of the Acoustical Society of America | volume = 105 | issue = 6 | pages = 3336–44 | doi = 10.1121/1.424662 ] Even sound levels as low as 40 dB(A) (about as loud as a refrigerator or library [cite web | url = http://www.chiltern.gov.uk/downloads/Decibel_chart_06  .pdf | title = Noise Facts and Figures! | format=PDF| accessdate = 2007-12-13 | publisher = Chiltern District Council] ) can generate noise complaints [cite book |author=Gelfand, Stanley A |title=Essentials of Audiology |publisher=Thieme Medical Publishers |location=New York |isbn=1-58890-017-7] and the lower threshold for noise producing
sleep disturbanceis 45 dB(A) or lower. [cite book |author=Walker, JR; Fahy, Frank |title=Fundamentals of noise and vibration |publisher=E & FN Spon |location=London |year=1998 |isbn=0419227008] Other factors that affect the 'annoyance level' of sound include beliefs about noise prevention and the importance of the noise source, and annoyance at the cause (i.e. non-noise related factors) of the noise.cite journal | first = JM | last = Field | title = Effect of personal and situational variables upon noise annoyance in residential areas | journal = Journal of the Acoustical Society of America | volume = 93 | issue = 5 | pages = 2753–63 | year = 1993 |doi = 10.1121/1.405851 | accessdate = 2007-12-13] Evidence regarding the impact of long-term noise versus recent changes in ongoing noise is equivocal on its impact on annoyance.
Estimates of sound annoyance typically rely on
weighting filters, which consider some sound frequencies to be more important than others based on their presumed audibility to the human ear. The older dB(A) weighting filter described above is used widely in the U.S., but underestimates the impact of frequencies around 6000 Hz and at very low frequencies. The newer ITU-R 468 noise weightingfilter is used more widely in Europe. The propagation of sound varies between environments; for example, low frequencies typically carry over longer distances. Therefore different filters, such as dB(B)and dB(C), may be recommended for specific situations.
When young children are exposed to speech interference levels of noise on a regular basis (the actual volume of which varies depending on distance and loudness of the speaker), there may develop speech or reading difficulties, because auditory processing functions are compromised.Fact|date=December 2007 In particular the writing learning impairment known as
dysgraphiais commonly associated with environmental stressors in the classroom.Fact|date=December 2007
noise regulations usually specify a maximum outdoor noise level of 60 to 65 dB(A), while occupational safety organizations recommend that the maximum exposure to noise is 40 hours per week at 85 to 90 dB(A). For every additional 3 dB(A), the maximum exposure time is reduced by a factor 2, e.g. 20 hours per week at 88 dB(A). Sometimes, a factor of two per additional 5 dB(A) is used. However, these occupational regulations are acknowledged by the health literature as inadequate to protect against hearing lossand other health effects
* [http://asa.aip.org/ Acoustical Society of America]
* [http://www.noiseandhealth.org Noise and Health] International Journal devoted to research on all aspects of noise and its effects on human health
* [http://www.ruidos.org/Noise/WHO_Noise_guidelines_contents.html World Health Organization: Guidelines for Community Noise]
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