Non-Auditory Physiological Effects

In addition to its effects on hearing, noise has also been implicated as having other physiological effects. Indeed, according to Ruback, Pandey, and Begum (1997), "individuals who complain about environmental stressors are probably also more likely to complain about other aspects of their life, including their health" (p. 29). Specifically, non-auditory physiological effects of noise pollution that have been identified thus far include cardiovascular, autonomic, and gastric effects. Further, it appears that noise can exert its non-auditory effects independent of hearing loss. For example, Peterson et al. (1981) effectively raised the blood pressure of rhesus monkeys by exposing them to elevated noise levels that did not decrease their auditory sensitivity.

The first category of non-auditory physiological effects includes effects on the cardiovascular system. In 1977, Knipschild and Oudshoorn indirectly demonstrated this effect by noting an increase in antihypertensive medication consumption in a village near an airport that correlated with an increase in aircraft traffic. A control village that was not near the airport did not demonstrate an increase in cardiovascular medication consumption during the same period.

The cardiovascular effects of noise have been the most abundantly researched non-auditory noise effects. According to Abel (1990), "loud noise. . . is purported to cause vasoconstriction with a consequent increase in blood pressure. This leads in turn to smooth muscle hypertrophy, narrower lumen in small vessels, and increased resistance to blood flow. The end result is hypertension" (p. 5). To investigate this effect, both laboratory and field studies have been conducted.

First, field studies have often been utilized to study the hypertensive effects of noise. These field studies can take place in either a community setting or an occupational setting. In an example of an occupational field study, Melamed and colleagues (1997) "studied the association between industrial noise exposure, noise annoyance, and serum lipid/lipoprotein levels in male. . . and female. . . blue-collar workers" (p. 292). The researchers concluded that "exposure to high industrial noise levels may be a risk factor for [cardiovascular disease] via increased plasma lipids" (p. 296), especially in younger male workers. Van Dijk, Verbeek, and de Fries (1987) and van Dijk, Souman, and de Vries (1987) also studied the non-auditory effects of noise in industrial occupational settings, but in neither case was a relationship found. In his review of occupational studies, van Dijk (1990) then concludes that "in about half of the studies a positive relation [between occupational noise levels and blood pressure] has been found. . . . Unfortunately, still no definite conclusions can be drawn" (p. 285). Thus, although occupational noise appears to be involved with cardiovascular disease, more research is needed before any definite conclusions can be drawn.

Community field studies have also attempted to demonstrate a relationship between noise and cardiovascular effects. For example, Otten, Schulte, and von Eiff (1990) studied healthy individuals who moved to residential areas in the city of Bonn that had either high traffic noise levels or low traffic noise levels. The results indicated that the people who moved to the noisier area were more likely to develop high blood pressure than the people who moved to the quieter area. Again, as in Melamed et al.'s occupational noise study discussed above, this relationship was stronger in males than in females. On the other hand, a study conducted by Pulles, Biesiot, and Stewart (1990) did not find a relationship between community noise and blood pressure. Thus, again it appears there may be a relationship between noise and cardiovascular effects, though the current research has proved somewhat inconclusive. Futher, Pulles et al. speculate that coping style may influence one's sensitivity to noise, while von Gierke and Harris (1990) speculate that attitude toward noise may be an influencing factor.

In addition to field studies, laboratory studies have also been conducted to study the relationship between noise and cardiovascular effects. An example of such as study includes one that was described by Abel (1990), in which volunteers were confined to a dormitory and exposed to pulsed tones over the course of 30 days. In this study, plasma cortisol and blood cholesterol levels increased with increases in noise beyond 85 dB, an effect that persisted for several days after the noise was ceased. Another study described in the same article found that diastolic but not systolic blood pressure was higher in subjects exposed to higher noise levels, an effect that was independent of family history of hypertension.

Autonomic effects have also been implicated in noise research, in addition to cardiovascular effects. For example, Levi (1966) found that urinary adrenaline and noradrenaline levels were higher in subjects who were exposed to short durations of noise and that in some cases "the changes bordered on the pathological" (p. 68). However, when exposed to similar noise levels over a relatively long period of time, adrenaline and noradrenaline levels changed very little. Thus, it appears that habituation may be involved in the autonomic effects of noise. Further, while in many cases noise levels do not appear to correlate with various hormonal activities (Burns, 1979), this area of study should not be overlooked.

Exposure to noise can lead to gastric changes, as well. For example, Bugliarello et al. (1976) describes a study in which exposure to 80 dB noise levels resulted in a reduction in stomach contraction strength. Additionally, Burns (1979) discuss the results of a study in which subjects who were unable to control their noise environment experienced increased gastrointestinal motility compared to subjects who could shut the noise off by pushing a switch. Thus, although research on this topic is somewhat sparse, it appears that noise can lead to changes in one's gastrointestinal system. And because gastric changes are related to ulcers, Bugliarello et al. (1976) and Bragdon (1972) both suggest that noise may be related to ulcer development, as well.

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