Noise (unwanted sound) is another not so pleasant feature of the urban environment. The U.S. Census Bureau reports that Americans cite noise – more than crime, litter, traffic, or inefficient government – as the biggest problem affecting their living environments. 138 million people in the US are regularly exposed to noise levels labeled as excessive by the Environmental Protection Agency. Noise clearly causes stress and can negatively impact mental and physical health. Noise has been shown to activate the sympathetic and endocrine systems (fight or flight). While many do what they can to avoid excessive noise, humans are not physiologically prepared to turn noise off ; people are wired to respond to sound for survival purposes. Noise leads to hearing fatigue and tinnitus; annoyance; interference with social behavior; interference with speech communication; sleep disturbance; decrements in school and work performance; psychiatric problems; fetal development problems; and cardiovascular disease.

Children are especially sensitive to noise. High levels of classroom noise have been shown to affect cognitive
performance. Reading and memory have been reported to be impaired in schoolchildren who were exposed to high levels of aircraft noise. Some studies have shown higher stress hormone levels and higher mean blood pressure readings in children exposed to high levels of community noise.

Roadways are responsible for most of the noise in urban environments, but airports have also been shown to be uniquely associated with noise related physical and mental health problems. Environmental noise regulations usually specify a maximum outdoor level of 60 to 65 decibels - dB(A), while occupational safety organizations recommend that the maximum exposure to noise is 40 hours per week at 85 to 90 dB(A). The threshold for sleep interference is 45 dB(A) or lower. One exposure to levels above 140 dB(A) can permanently damage hearing. The following are the decibel levels of common noise exposures:
 
• 0 dBA: softest sound a person can hear with normal hearing
• 10: normal breathing
• 20: whispering at 5 feet
• 30: soft whisper
• 40: quiet residential area
• 50: rainfall
• 50: large office 
• 60: normal conversation
• 70: freeway traffic
• 75: washing machine
• 80: alarm clock
• 80: ringing telephone
• 85: vacuum cleaner
• 85: noisy restaurant
• 90: blender
• 90: truck
• 95: hair dryer
• 110: shouting in ear
• 110: crying baby
• 110: motorcycle
• 115: subway
• 120: thunder
• 120: jet plane (at ramp)
• 120: ambulance siren
• 120: rock concert
• 166: handgun

Reducing the number of cars on the road here will help our ever worsening noise problem. Riding your bike to wrok once a week is a "sound" way to make the noise less noisy.