Damage to hearing and stress reactions
Human beings are equipped with a highly sophisticated sensor that is able to perceive sound. This sensor is the ear and its downstream processing levels in the brain. This sensor is never switched off, even when we sleep. We experience sound as noise in settings where it is disturbing, stressful, or harmful.
Hearing damage and stress responses
Excessive acoustic input, whether too loud or too long, can provoke irreversible health problems, including hearing damage secondary to lengthy acoustic events or brief acoustic peaks (aural syndrome). Such damage can range from impaired hearing to deafness, as well as brief or chronic tinnitus (ringing in the ears). High acoustic levels occur not only at workplaces, but also in leisure time settings such as pop concerts.
In addition, sound or noise can affect the organism as a whole by provoking physical stress responses (extra-aural syndrome). Such responses can also be provoked by low levels of environmental sound such as traffic noise that do not cause hearing damage.
The psychosocial stress effects of noise affect more than just our sense of well being and our quality of life; for noise can affect our general state of health as well in that it activates our autonomous nervous system and hormonal system. This can provoke hypertension, increased cardiac frequency (racing heart) and other cardiovascular changes, leading to metabolic disturbances secondary to a rise in stress hormone excretion. Because our circulatory and metabolic processes are regulated by the autonomous nervous system for the most part below the level of consciousness, autonomous responses also occur while we sleep and in individuals who claim to have grown accustomed to noise.
Chronic effects of noise pollution
Apart from hearing damage, the chronic effects of long term exposure to noise pollution can provoke (a) changes in biological risk factors such as blood lipids, blood sugar and coagulation factors; and (b) cardiovascular disorders such as arteriosclerosis, hypertension and heart attacks.