Noise & health
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Comparative Study
Stress effects of noise in a field experiment in comparison to reactions to short term noise exposure in the laboratory.
Reactions to noise-induced communication disturbance of 42 men during a seminar were investigated. Stress reactions with or without road traffic noise (Lm = 60 dBA) were compared. Traffic noise was played back via loudspeakers during one day in the seminar room. ⋯ There existed a positive correlation between noise sensitivity and the systolic blood pressure increases during the seminar, whilst the correlation, between noise sensitivity and systolic blood pressure increases in the laboratory exposure, was negative. From these results we conclude that short-term noise exposure experiments do not provide information about the effects of long-term real life exposure to environmental noise. Potential health effects of chronic noise-induced disturbances of activities are discussed.
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Traffic noise is the most important source of environmental annoyance. According to the Environmental Expert Council of Germany, severe annoyance persistent over prolonged periods of time is to be regarded as causing distress. Previously, extraaural noise effects were mostly assessed using a paradigm in which the sound level played the major role. ⋯ However, according to the Environmental Expert Council, these studies show a consistent trend towards an increased cardiovascular risk if the daytime immission level exceeds 65 dB(A). Most of the previous studies on the extraaural effects of occupational noise have been invalidated by exposure misclassifications. In future studies on health effects of noise a correct exposure assessment is one of the most important preconditions.
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Mainly dependent on level and dynamic increase sound produces over-shooting excitations which activate subcortical processing centers (e.g. the amygdala, functioning as fear conditioning center) besides cortical areas (e. g. arousing annoyance, awakenings) as well. In addition there exist very close central nervous connections between subcortical parts of the auditory system (e.g. amygdala) showing typical plasticity effects (sensitization) and the hypothalmic-pituitary-adrenal (HPA)-axis. Using that causal chain noise induce cortisol excretion even below the awakening threshold. ⋯ This fact and the unusual large permeability of cortisol through the cell membranes opens a wide field of connections between stress-dependent cortisol production and the disturbance of a large number of other endocrine processes, especially as a result of long-term stress activation by environmental influences such as environmental noise. Based upon a physiological model calculating the cortisol accumulation starting at a nightly threshold of physiological over-proportional reactions around Lmax = 53 dB(A) the number of tolerable noise events (over-flights in a nightly time range) can be estimated for given indoor peak sound pressure levels, keeping the cortisol increase within the normal range. Examples of results for 8 hours in the night are for instance number and level combinations (NAL-values) of 13 events with 53 dB(A) indoor peak level or 6 events with 70 dB(A) indoor peak level respectively.
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World wide rules for sleep staging originate to 1967. Since then many investigations aimed to give numbers for the degree of sleep disturbances due to air traffic noise. But the variables used, such as the amount of relative sleep stages, total sleep time, or sleep efficiency, could not explain impairment in health and performance sufficiently. ⋯ Environmentally related sleep disturbances are described, EEG and vegetative (micro)-arousals, and the actual knowledge in sleep medicine is given in terms of the international classification of sleep disorders (ICSD). The effects on health, and disturbed performance capacity during the day are shown by self ratings of 160 patients. Elevated metabolic rate caused by micro-arousal and/or insomnia, may play an additional role in health impairment.
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In noise effect research often the awakening reaction is maintained to be the only important health related reaction. The main argument is that sleep represents a trophotropic phase ("energy storing"). In contrast to this awakening reactions or lying awake belong to the ergotropic phase ("energy consuming"). ⋯ These circadian rhythms of sleep and neuroendocrine regulation are necessary for the physical as well as for the psychic recovery of the sleeper. Noise exposure during sleep which causes frequent arousal leads to decreased performance capacity, drowsiness and tiredness during the day. Long-term disturbances of the described circadian rhythms have a deteriorating effect on health, even when noise induced awakenings are avoided.