| Noise Health Effects |
Article Index for Noise |
Website Links For Noise |
Information About ™Noise Health Effects |
| CATEGORIES ABOUT NOISE HEALTH EFFECTS | |
| health sciences | |
| noise pollution | |
|
HEARING LOSS The Pinna (visible portion of the human Ear ) combined with the Middle Ear amplifies Sound levels by a factor of 20 when sound reaches the Inner Ear Approximately ten percent of the population in industrialized societies have significant populations were tracked, with the result that noise-exposed persons had much greater hearing loss than their Age Cohorts who were relatively unexposed to noise. In fact, it has been shown that people in non-industrialized countries do not experience the same progressive hearing loss S. Rosen and P. Olin, ''Hearing Loss and Coronary Heart Disease '', Archives of Otollaryngology , 82:236 (1965). The mechanism of intake. In 1972 the U.S. EPA told Congress that at least 34 million people were exposed to sound levels on a daily basis that are likely to lead to significant hearing lossSenate Public Works Committee, Noise Pollution and Abatement Act of 1972, S. Rep. No. 1160, 92nd Cong. 2nd session. The worldwide implication for industrialized countries would place this exposed population in the hundreds of millions. CARDIOVASCULAR DISEASE AND OTHER HEALTH EFFECTS There are important cardiovascular consequences from elevated sound levels, principally because the elevated Adrenaline levels trigger a narrowing of the blood vessels ( Vasoconstriction ). Sound levels, again of fairly typical roadway noise exposure, are known 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. (Independently, high noise levels are known to produce Medical Stress reactions, another risk associative with Cardiovascular Disease .) Noise induced medical stress is significant for two reasons. First, it is often prolonged exposure for eight to 16 hours per day, leading to elevated Blood Pressure for much of the day. Second, unlike emotional stress, it has a very clear effect on the blood pressure, whereas this is not always the case with emotional stress. These effects may also be compounded by other environmental vasoconstrictors such as Over-illumination or Light Pollution . Other proven effects of high noise levels are increased frequency of and not merely from Birth . The Fetus is 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 Organ s and the Central Nervous System are formed. Later developmental effects occur as vasoconstriction in the mother reduces blood flow, and hence Oxygen and nutrition to the fetus. Low birth weights and noise were also associated with lower levels of certain Hormone s in the mother, these hormones being thought to affect fetal growth and to be a good indicator of Protein production. The difference between the hormone levels of pregnant mothers in noisy versus quiet areas increased as birth approached. PSYCHOLOGICAL EFFECTS Earlier researchers often grouped the non-physiological impacts of noise as “annoyance”. As research unfolded, it became clear that there are a host of , Reading Development in children, Stress , Mental Health (including disengagement and increases in aggressive behavior). These effects are statistical but measurable changes in a population of individuals compared to a control group of persons in a quiet environment. Obviously, other negative environmental factors are likely to be present in high noise areas such as higher air pollution levels and possibly Poverty -induced Nutrition deficits; however, the overwhelming weight of dozens of independent studies identify Noise Pollution to be responsible for significant increases in the psychological effects studied above. Measurements of noise annoyance typically rely on Weighting Filters , which consider sound frequencies annoying only to the degree that they are audible, on average, to a human ear at a particular decibel volume. Common methods include the older dBA weighting filter used widely in the U.S., which underestimates the impact of frequences around 6000 Hz and at very low frequencies, and the newer ITU-R 468 Noise Weighting filter, which is used more widely. It is important to note that these filters do not necessarily reflect the occurrence of adverse health effects from noise, which may not depend on its audibility to the ear, nor do they take into account the propensity of low-frequency noises to penetrate into buildings or to carry over long distances. Annoyance effects of noise vary greatly by demographics and by the perception of how useful the entity is that originates the noise. For example, aircraft mechanics who live near an airport are less likely to be complainants, since their livelihood is based upon airport operations. Annoyance is also influenced by whether the noise source is visible, whether it has pure tones or hammer effects and whether the recipient believes the noise can be controlled. In any case, the onsetH.M.E. Miedema and H. Vos, ''Exposure response relationships for transportation noise'', Journal of the Acoustical Society of America, 105, 3336-44 of noise complaints can be as low as 40 dB(A) Stanley A Gelfand, ''Essentials of Audiology'', Theime Medical Publishers, New York, N.Y. (2001) ISBN 1588900177. Whether the noise occurs at night is another critical variable for annoyance phenomena. Most commonly, concerted actions of the public appear at approximately 65dBA regarding roadway, aircraft or industrial noise in the environment. Closely associated with annoyance are Sleep Disturbance and speech interference phenomena. The threshold for sleep interference is 45 dB(A) or lowerF Fahy and J Walker, ''Fundamentals of Noise and Vibration'', Spon Press, UK (2001). The onset of Speech Interference is about 63dBA, or roughly the sound level of speech in a normal tone between two people separated by one meter. When young children are exposed to speech interference levels of noise on a regular basis, there is a likelihood of developing speech or reading difficulties, because the auditory processing functions are compromised. In particular the writing learning impairment known as Dysgraphia is commonly associated with environmental Stressor s in the classroom. Effects of environmental noise upon aggression, mental health, anxiety, withdrawal and other psychological factors have been studied by numerous researchers. For example J.M.. FieldJ.M. Field, ''Effect of personal and situational variables upon noise annoyance in residential areas'', Journal of the Acoustical Society of America, 93: 2753-2763 (1993) examines a variety of these outcomes and finds significant influence of moderate level environmental noise upon human behavior and mood. There are also strong associative impacts when other stressors are present such as Over-illumination and presence of certain drugs. REGULATIONS Main article: Noise Regulation Environmental noise regulations usually specify a maximum outdoor level of 60 to 65 DB(A) , while occupational safety organisations 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 Loss and other health effects discussed above. REFERENCES SEE ALSO |
|
|