Noise environments outdoors and the effects of community noise exposure

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, has gained substantial acceptance as a measure of community noise exposure, During the same period, the effects of various levels of noise exposure on human activities and health have been widely studied, Data from many social surveys have been brought together and analyzed to clarify the relationship between noise exposure and the prevalence of annoyance which provides a broad indication of the impact of intrusive noise on human communities, Criteria and guidelines based on such studies are now widely used in urban planning and their effectiveness is enhanced by new standards that characterize sound propagation outdoors, Regulations that control motor vehicle noise at the source have, as yet, produced only limited benefits, while highway barriers provide some relief from excessive exposure to traffic noise. In recent years, there have been impressive reductions in the noise emissions from commercial aircraft and notable improvements in the control of airport noise, Finally, the potential effects of noise on wildlife, especially endangered species, now come under close scrutiny when noise-generating projects are planned in sensitive environments.