Edgar A. G. Shaw
Inst. for Microstructural Sci., Natl. Res. Council, Ottawa, ON K1A 0R6, Canada
Man-made noise, especially transportation noise, creates acoustical environments that are vastly different from those associated with pristine habitats. During the past 25 years, the day--night average sound level, L[sub dn], has gained substantial acceptance as a valid measure of the magnitude of any given pattern of community noise, taking into account its complex temporal and spectral characteristics. During the same period, the effects of various levels of noise exposure on human activities and well-being have been widely studied. Data from many social surveys have been brought together and analyzed to clarify the relationship between noise level and the prevalence of annoyance which provides a broad indication of the impact of intrusive noise on human communities. Criteria based on such studies are now widely used in urban planning. In recent years, there have been impressive reductions in the noise emissions from commercial aircraft and notable improvements in the control of airport noise, while highway barriers now provide some relief from motor vehicle noise. Finally, the potential effects of noise on wildlife, especially endangered species, now come under close scrutiny when major projects are planned in remote areas.