Monday, December 31, 2012

Stress and Noise


Even sounds you can't hear can have a powerful affect on your nervous system. One example is the "infrasound" in the roar of a tiger.

A tiger's intimidating roar has the power to paralyze animals. Even experienced human trainers are stunned. "We suspect that this is caused by the low frequencies and loudness of the sound," says Elizabeth von Muggenthaler, a bioacoustician from the Fauna Communications Research Institute in North Carolina. "Humans can hear frequencies from 20 hertz to 20,000 hertz, but whales, elephants, rhinos, and tigers can produce sounds below 20 hertz."


Not just loud or sudden noises provoke a stress response. Chronic low-level noise also negatively influences the brain and behavior. Whether from the road or in the office, low-intensity noise has a subtle yet insidious effect on our health and well-being.

Noise at home or school can affect children's ability to learn. Compared to kids from quieter neighborhoods, children living near airports or busy highways tend to have lower reading scores and develop language skills more slowly. Psychiatric hospitalizations are higher in noisy communities. Bad moods, lack of concentration, fatigue, and poor work performance can result from continual exposure to unpleasant noise.

According to Dr. Alice H. Suter, an audiologist at the National Institute for Occupational Safety and Health: "Included in noise-related problems are high blood pressure, peptic ulcers, cardiovascular deaths, strokes, suicides, degradation of the immune system, and impairment of learning. Noise is also associated with an increase in aggression and a decrease in cooperation."

Even everyday traffic noise can harm the health and well-being of children. In the first study to look at the non-auditory health effects of typical ambient community noise, it was shown that chronic low-level noise from local traffic raised levels of stress hormones in children, as well as their blood pressure and heart rates.

"We found that even low-level noise can be a stressor. It elevates psychophysiological factors and triggers more symptoms of anxiety and nervousness," says environmental psychologist Gary Evans of Cornell University, an international expert on environmental stress, such as noise, crowding, and air pollution.


Women respond differently to loud noise, too. A study at Texas A&M University found that "women have a lower threshold to experience noise as stressful," according to psychologist Dr. Mary W. Meagher. "Our data suggest that women may be more sensitive to noise stress than men."


"The U.S. Census Bureau reports that Americans cite noise – more than crime, litter, traffic, or inefficient government – as the biggest problem affecting their neighborhoods. 138 million people are regularly exposed to noise levels labeled as excessive by the Environmental Protection Agency."8

British investigators found that a greater amount of neighborhood problems, including noise, was associated with residents being three times as likely to say their physical function was impaired and twice as likely to report poorer health. "What we think is happening is that neighborhood stress influences the biological processes that promote disease risk," said Dr. Andrew Steptoe of University College London.

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