An excessive amount of sound, whether in terms of intensity or of duration, can have lasting adverse effects on health or cause physiological damage. Sound has an effect on the whole organism, inasmuch as it triggers stress reactions (extra-aural effects). These effects can manifest even through exposure to low level non-harmful levels of sound encountered in the environment, for example, traffic noise.
As a psycho-social stress factor, noise activates the sympathetic nervous and hormonal systems. Consequent upon this are changes in blood pressure, heart rate, and other circulatory factors. The body generates increased levels of stress hormones, which in their turn affect the metabolic functions. Circulation and metabolism are mostly regulated by the sympathetic nervous system without conscious intervention. The autonomous reactions which occur therefore also arise in sleep and in people who consider themselves to be inured to noise.
Possible long-term consequences of chronic noise exposure include, in addition to damage to hearing, other changes in respect of biological risk factors (e.g. blood fat, blood sugar, clotting factors) and circulatory disease such as arteriosclerotic changes (“arterial calcification”), high blood pressure, and certain heart diseases including heart attacks.
Increased risk of high blood pressure
In the research project „Epidemiological investigations into the influence of noise-related stress on the immune system and the occurrence of arteriosclerosis”, the Federal Environment Agency ( Umweltbundesamt - UBA ) investigated more than 1,700 predominantly older people from Berlin. The evaluation showed that people living in noisy areas were more frequently receiving treatment for high blood pressure than those from relatively quiet areas. Thereby, people who were exposed to night time levels of 55 decibels (dB(A)) or higher directly outside their bedroom window were almost twice as likely to be receiving treatment for high blood pressure than those who were exposed to levels of noise of below 50 decibels.
In addition, statistical correspondences were established between night time traffic noise exposure at home and deleterious effects on the immune system and metabolic functions. In contrast to the noise exposure during the night, the relationship between the noise exposure during daytime and medical treatment for the above complaints was less marked. The frequency of medical treatment for psychological disorders, however, was in close relation to the subjectively experienced annoyance due to daytime noise exposure.
The results of the research showed that the human organism reacts more sensitively to noise when at rest during the night than during the diurnal active phase. It also became clear how important noise abatement measures are during nocturnal rest phases if adverse health effects are to be avoided.
Higher risk of heart attack
The relationship between environmental noise, noise in the work place, and heart attacks (myocardial infarction) were investigated in the Noise and Risk of Myocardial Infarction study („Chronischer Lärm als Risikofaktor für den Myokardinfarkt – ‚NaRoMI’-Studie “), which was carried out on behalf of the Federal Environment Agency and the Federal Institute for Occupational Safety and Health ( Bundesanstalt für Arbeitsschutz und Arbeitsmedizin ). The scientists surveyed 4,115 patients in Berlin clinics in a “case-control study”. Each heart attack patient was matched with one control patient (or, in the case of women, two control patients) of the same age, who was having treatment for a non-noise related condition, for example, as a result of an accident. The result showed that the coronary patients tended more frequently to live on noisy streets than the control patients. This was particularly in evidence when only those who had been living at the same address for a longer period of time – at least ten years – were taken into consideration. In addition, a clear relation between “dose” and “effect” was established: men in noisy homes (with an average daily exposure of more than 65 decibels outside the home) were 20 to 30 per cent more at risk of having a heart attack (myocardial infarction) than men from quieter residential areas (with an average daily exposure of up to 60 decibels). In the case of women, no clear relation could be established between heart attack risk and exposure to traffic noise. The various different activities carried out by men and women in the course of the day may well play a role here; in addition, statistical distortions brought about by unknown menopausal status and hormone therapy, which was not included in the scope of the survey, may have arisen.
The specialists were unable to establish any exposure-response association between noise exposure in the work place and the risk of myocardial infarction. A higher risk was observed in the case of moderate noise exposure, but not in that of very high sound levels. This may be due to the well-known “healthy worker effect” by which people with chronic health conditions may well have made a conscious decision to avoid noisy work places (self selection).
The results of the study added weight to the supposition that noise exposure increases the risk of heart attacks. It may well be the case that traffic noise has a particularly deleterious effect on health when combined with other everyday stress factors, not necessarily just those related to noise.
The Federal Environment Agency has assessed the results of various epidemiological studies on the effects of noise by means of a critical literary overview, and has also compiled those results in a meta-analysis. The Agency has by these means derived an exposure-response curve, which can be used for quantitative risk estimation and analysis. Such risk estimations have a major part to play in decisions relating to environmental and health policy. The results of the meta-analysis are contained within the English-language research document “Transportation Noise and Cardiovascular Risk ”. According to this report, it may be justified to come to the unhappy conclusion that around three per cent of all cases of heart attack in Germany are caused by road traffic noise.
If at all possible, bedrooms should be located in a part of the home not directly exposed to traffic noise. Ear plugs can help to reduce sleep deprivation due to environmental noise. Improved sound insulation (closing windows or fitting windows with better sound insulation properties) can help to prevent noise exposure in indoor areas. Adequate ventilation can be assured from neighbouring rooms or by the use of acoustic glazing with reduced-noise ventilation systems. It is however the task of environmental policy as far as possible to prevent harmful noise from arising in the first place.