Noise Effect

What does noise affect?

 

One of the main effects of aircraft noise on communities surrounding airports is long-term annoyance.

The scientific community adopted the use of long-term annoyance as its primary gauge of community response. This is because it attempts to account for all negative aspects of effects from noise. Some examples are:

  • Increased annoyance due to being awakened the previous night by aircraft
  • Interference with everyday conversation

Studies of Long-Term Community Annoyance

Several laboratory and field studies have been carried out to measure annoyance. These studies accounted for differences in each person's individual circumstances and preferences. Laboratory studies have helped isolate a number of the contributing factors. These include the:

  • Intensity level and spectral characteristics of the noise
  • Duration of the noise
  • Presence of impulses
  • Pitch of the noise
  • Information content of the noise
  • Degree of interference with activity

Ways to Measure Long-Term Community Annoyance

Social surveys were used to develop general "dose-response" relationships. These are used to estimate the amount of people who will be highly annoyed by a particular noise level. The land use criteria developed from these studies are used around the world.

In these surveys, one of the most used measurements is the percentage of people expected to be "highly annoyed". A wide variety of responses have been used to determine:

  • intrusiveness of noise
  • disturbances of speech, sleep, audio/video entertainment, and outdoor living

People are asked to rate their annoyance about noise on a numerical scale. For example on a five point scale, the choices are usually "not annoyed", "slightly annoyed", "moderately annoyed", "very annoyed" and "extremely annoyed".

A researcher named Schultz combined the top two phrases on the scale ("very annoyed" and "extremely annoyed") into the phrase "highly annoyed". "Highly annoyed" respondents are those whose annoyance fell within the upper 28% of the scale. This definition of "percent highly annoyed" (%HA) is used to develop Federal policy on environmental noise.

Other factors may also influence an individual's annoyance:

  • Emotional Factors
    • Feelings about the necessity or preventability of the noise
    • Judgment of the importance and value of the activity that is producing the noise
    • Activity at the time an individual hears the noise
    • Attitude about the environment
    • General sensitivity to noise
    • Belief about the effect of noise on health
    • Feeling of fear associated with the noise
  • Physical Factors
    • Type of neighborhood
    • Time of day
    • Season
    • Predictability of noise
    • Control over the noise source
    • Length of time an individual is exposed to a noise

Additional surveys studied the relationship between the Day-Night Average Sound Level (DNL) and percentage "Highly Annoyed" for three transportation noise sources:

  • aircraft traffic
  • road traffic
  • railway traffic

For a DNL of 65 dB, the percent of the people forecasted to be "Highly Annoyed" is:

  • 28% for air traffic
  • 18% for road traffic
  • 11% for railroad traffic

Aircraft noise seems to produce a stronger annoyance response than road traffic. However, interpreting data from different studies can be tricky. The World Health Organization (WHO) noted that five major factors should be considered:

  • personal factors
  • demographic factor
  • lifestyle factors
  • the duration of noise exposure
  • the population experience with noise

Further research into understanding the differences in transportation noise perception is needed.

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