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Definitions

We live in an environment filled with sound.  The devices and systems that society uses to improve our quality of life often emit sound.  When the sounds become unwanted they are called noise.  Unreasonable or excessive noise is considered noise pollution. 

Technological improvements in our lives have sometimes resulted in more and new types of noise pollution, but noise has always been a community issue.  One hundred years ago before the proliferation of automobiles, aircraft, and mass-transit, noise was considered one of the most significant environmental concerns in the New York city communities. Since then transportation noise has come to predominate our lives and noise is still a major concern. 

 Since mankind has lived in communities, noise has always been in issue. It's the type and degree of noise that keeps changing and our perception of sound.  Noise is not always a man-made phenomena.  Natural environments are full of sound, some are considered beautiful, others a nuisance.  Good examples of sounds that are considered both beautiful and annoying are wildlife sounds, such as birds chirping.

What sounds are considered noise and at what level is the sound annoying is a perception issue. No particular sound level predisposes an impact (an annoyance condition) since people rely on a variety of parameters to judge sound quality.  The sound levels produced by insects flying near us are extremely low, yet they typically produce a negative reaction. The sound levels produced by waves crashing on the beach are high (easily over 70 dBA), yet people find them comforting.

Physical Characteristics

How people perceive any given sound depends on several measurable physical characteristics of the sound.  These factors are:
 

  • Intensity:  Sound intensity is often equated to loudness.  The sound level magnitude (typically measured in decibels) is a measure of sound intensity.  A 10 decibel increase in intensity is generally perceived as a doubling in loudness.
  • Frequency Content:  Most common sounds are comprised of acoustic energy distributed over a variety of frequencies.  Acoustic frequencies, commonly referred to as tone or pitch, are typically measured in Hertz (Hz).  Pure tones (such as those generated by a tuning fork) have all their energy concentrated in a narrow frequency range.  High-frequency sound (above 2,000 Hz) is typically considered more annoying than low-frequency sound (below 500 Hz) and may also be perceived as louder.
  • Temporal Pattern:  The temporal nature of sound includes factors such as continuity, fluctuation, impulsiveness, and intermittence.  Sound with increasing intensity is often perceived as louder than sound with decreasing intensity.  Impulsive and intermittent sounds are usually perceived as louder than the actual sound level.


Noise by definition is unwanted sound.  What type of sounds are unwanted, when or what level is not tolerable, are subjective decisions that each person makes at that time and over time.  Research confirms that the human response to noise is subject to considerable variability.  There are many factors, both emotional and physical, which contribute to the variation in human reaction to noise.  The existence of numerous emotional and physical variables prohibits defining an exact individual or community response for any given noise level.  Community noise criteria are therefore based on statistical averages of human response to noise and applicable health criterion.
 

 For more information about the factors involved in the human reaction to noise:
The Human Factors

The EPA has published information which describe noise “cause and effect” relationships for sensitive land uses.  These relationships are not standards because they do not account for the cost or feasibility of achieving these levels.  These relationships are provided for comparative purposes. 
For more information about the EPA cause and effect relationships:
EPA Cause and Effect Table