4.1 Evaluation of Environmental Noise—Environmental noise is evaluated by comparing a measurement or prediction of the noise to one or more criteria. There are many different criteria and ways of measuring and specifying noise, depending on the purpose of the evaluation.
4.2 Selection of Criteria—This guide assists in selecting the appropriate criteria and measurement method to evaluate noise. In making the selection, the user should consider the following: purpose of the evaluation (compatibility, activity interference, aesthetics, comfort, annoyance, health effects, hearing damage, etc.); type of data that are available or could be available (A-weighted, octave-band, average level, maximum level, day-night level, calibrated recordings including .wav files from which various measurements could be made, etc.); available budget for instrumentation and manpower to obtain that data; and regulatory or legal requirements for the use of a specific criterion. After selecting a measurement method, the user should consult appropriate references for more detailed guidance.
4.3 Objective versus Subjective Evaluations—The overall sound environment as perceived outdoors is often called a soundscape. Soundscapes have both objective (quantitative) and subjective (qualitative) attributes. This guide is limited to the objective measurement and evaluation of sound found outdoors though the criteria used may be influenced by qualitative factors. Current soundscape research involves evaluation methods and criteria that rely extensively on qualitative factors, both acoustical and non-acoustical, while including requirements for quantitative sound measurement. Two basic tenets of quantitative soundscape measurements are that the ambient sound at a location is comprised of a combination of specific acoustic events that can be measured individually and in combinations; and that the sounds should be measured using methods that represent the ways in which they are heard by people. (1)6
1.1 This guide covers many measurement methods and criteria for evaluating environmental noise. It includes the following:
1.1.1 The use of weightings, penalties, and normalization factors;
1.1.2 Types of noise measurements and criteria, indicating their limitations and best uses;
1.1.3 Sources of criteria;
1.1.4 Recommended procedures for criteria selection;
1.1.5 A catalog of selected available criteria; and
1.1.6 Suggested applications of sound level measurements and criteria.
1.2 Criteria Selection—This guide will assist use......
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