Environmental Engineering Reference
In-Depth Information
4.1 Introduction
In identifying the many sources of noise, Annette Zaner [1] noted that although
noise has intruded on people for thousands of years, it was the Industrial Revolution
and the rise of cities that accelerated the growth of noise pollution. She went on to
say that noise producing and noise-related technology were advancing so rapidly
that it was difficult to catalogue noise sources. One might expect that continued
advances in technology would make noise even more ubiquitous; this has proven
to be the case. Apart from technology, the United States Environmental Protection
Agency (EPA) documented that noise levels in communities were directly related to
population density. Noise from road, rail, and air traffic, construction sites, house-
hold appliances, and from an increasing number of highly mobile, powerful, and
varied noise polluting devices has contributed to this growth in noise [2-5]. Thus,
population growth, progressive urbanization, and technology all contribute to cur-
rent noise levels. Some people view noise as a nuisance, accepting this nuisance
as the price we pay for living in the modern world. Others, and their numbers are
increasing, are concerned about the growing evidence that noise can lead to adverse
physiological and psychological effects that degrade both health and well-being.
Dr. William H. Stewart, former Surgeon General, stated, “Calling noise a nuisance
is like calling smog an inconvenience. Noise must be considered a hazard to the
health of people everywhere” [5].
Despite Dr. Stewart's comments, made 30 years ago, health professionals, envi-
ronmentalists, educators, and government agencies have not moved as assertively
as they should have in curbing noise. In turn, legal and administrative actions,
educational efforts, and technological advancements to control noise have lagged
behind. To encourage the desire in readers of this chapter to engage in activi-
ties that will lessen environmental noises, it will be necessary for them to learn
about the differences between sound and noise, why people react negatively to
noise, and how noise can adversely influence physiological and psychological well-
being. Just as technology has contributed to the increase in the noise around us,
it is hoped that this chapter will promote technologies that will lower the noise
level.
4.2 Defining Sound and Noise
Sound begins as a vibrating object causes the movement of air molecules, setting
up alternate bands of compression and expansion in the air that then strike the ear
drum. The mechanisms of the middle ear carry the vibrations to the hair cells of
the inner ear (the Organ of Corti) where they are converted into electrical impulses
that are transmitted to the brain. The brain decodes these transmissions into what
we perceive as sound - its nature, pitch, volume, source, and duration. The brain
also provides emotional evaluation of the sound. In other words, the listener can
determine what the sound represents and whether the sound evokes pleasure or
