The loudness of noise is measured in decibels and ranges
from 0 to around 140 decibels . Some people can hear below
the zero level. The frequency of sound is measured in Hertz
(Hz) (cycles per second). The human ear cannot hear all frequencies.
Normal hearing ranges from 20 Hz to 20,000 Hz.
When a person is exposed to noise pollution, certain stress
hormones are released throughout the body. Some of these are
adrenaline, cortisol, and others. The longer these hormones
circulate throughout the body, the more likely they are to
cause certain psychological problems that may be life threatening.
Some problems caused by noise pollution are hypertension,
heart failure, stroke, and certain problems in the immune
system. Stressed people tend to eat unhealthily, smoke more,
and exercise less. This can eventually lead to heart disease.
Noise pollution increases the heart rate which can lead to
heart attack. Noise pollution also leads to increased cholesterol
which can also lead to a heart attack or stroke.
The WHO's Working Group on the Noise Environmental Burden
on Disease found that two percent of Europeans suffered from
severely disturbed sleep due to noise pollution and 15 percent
of Europeans suffer from severe annoyance due to noise pollution.
It was also discovered that three percent of all Tinnitus
cases were results of noise pollution. Tinnitus is a condition
in which the affected person hears sounds that no else hears.
It was also found that if a person is chronically exposed
sounds of 50 db or higher at night-time, then they are prone
to chronic cardiovascular problems. The threshold for sleep
disturbance is 42 db. The threshold for general annoyance
is 35 db. Another affect of noise pollution on humans is tightness
in the muscles.
Noise pollution affects the human ear and the brain. This
is why people might frequently get a headache when exposed
to loud noises. This can also affect a person psychologically.
One of these effects is increased stress.