Evolution did not equip you to live in a world of constant noise. Your nervous system was engineered by natural selection for an environment of almost total quiet. Nature is mostly filled with soft, quiet sounds: leaves rustling, water trickling, insects buzzing. An animal call here and there. This is what your amygdala (the fear center in the brain) rates as a normal sound level. Sharp sounds, loud bangs, people yelling and crying, revving engines and the like all trigger a fear/danger response.
Noise activates the body’s stress reaction, and living in an environment of chronic noise pollution leads to a condition of chronic stress. Research shows too much noise can lead to high blood pressure, heart disease and stroke. It interrupts our natural sleep cycles, which creates even more stress. And stress lowers immunity, opening us up to illness in general. Children, in particular, are negatively affected by sound pollution, which has been proven to lower reading skills and impair memory.