Acoustics Information
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Noise Impact and Regulation
The noise impact that results from a new or modified development depends on several factors, notably the change or increase in ambient or background sound levels that will result. Noise standards and guidelines have been promulgated by a wide range of organizations and institutions spanning from the World Health Organization, federal and state governments, to local municipalities. The objective of these standards and guidelines is to protect people from adverse impact related to a variety of noise sources including transportation and industrial noise in particular.
The World Health Organization (WHO) published Community Noise Guidelines in 1999 that provide acceptable indoor and outdoor sound levels for various land uses and settings. The WHO guideline for outdoor nighttime sound levels is an annual average of 45 dBA based on an eight-hour nighttime period. WHO anticipates that this will result in an indoor sound level of 30 dBA at night. The WHO guidelines also state that special consideration should be given to areas of very low ambient sound levels and for sound levels containing significant contribution of low frequency sound, however, no quantified adjustments are provided.
In 2009, the WHO Regional Office for Europe published “Night Noise Guidelines for Europe” as an extension and update of the 1999 Community Noise Guidelines. This was accomplished by a working group of experts and stakeholders from industry and other recognized organizations. A nighttime noise guideline of 40 dBA was established as a target to protect the public including groups most vulnerable to noise impact such as the chronically ill and the elderly. As with the 1999 Guidelines, this target is based on the annual nighttime average sound level. An interim target of 55 dBA was also established where the night guideline cannot be achieved in the short term.
In Maine, the State Department of Environmental Protection establishes sound level limits for developments as part of its Site Location of Development Law Regulations. The Maine DEP regulation Chapter 375.10 specifies sound level limits based on land use and existing ambient sound levels. For rural areas, the quietest limits of 55 dBA daytime and 45 dBA nighttime for hourly equivalent sound levels (LAeq) usually apply. Maine DEP nighttime limits apply up to 500 feet from a residence on a protected location so that the resulting sound levels at the residence will be below the limit. Beyond 500 feet, the daytime limit applies 24 hours a day. In contrast to WHO guidelines, the Maine DEP regulation applies sound level limits on an hourly basis with no averaging over daytime, nighttime or longer periods. There are also special provisions and “penalties” that apply when the sound level generated by a development results in a tonal or short duration repetitive sound.
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