THE SCIENCE AND APPLICATIONS OF ACOUSTICS - H. H. Arnold ...

13.10 Evaluation of Traffic Noise 335became apathetic to the noise, or the background noise arising from surface traffic,construction or operation of industrial facilities had increased sufficiently to maskmore of the aircraft noise.The use of NNI was superseded in the United Kingdom in 1988 in favor ofmeasurements based on the A-weighted L eq (cf., Equation (13.6)). This parameteris averaged over the period from 0700 to 2300 h (7 a.m. to 11 p.m.). The measureL dn of Equation (13.7) is not applied because nighttime flights are severely limitedin the United Kingdom. Both Switzerland and Ireland still make use of NNI.Equivalent Sound LevelWhile some nations continue to use NEF or NNI as descriptors, it has been establishedthat L eq and L dn are much simpler to measure and to evaluate since theyseem to correlate well with subjective response. In addition to the United Kingdomwhich uses only L eq over an 18-h period (since nighttime flights are restricted),both Germany and Luxembourg have adopted the L dn method with (0600–2200 h)day and (2200–0600 h) night classifications. In the United States, as the result ofthe publication of EPA Report 550/9-74-004 in 1974 and similar documents, theuse of CNR and NEF has been well superseded by the day–night equivalent levelDNL for rating of potential impacts of noise and for planning purposes and landusage near military and civilian airports. In fact, a directive (Part 256 of Title 32of the Code of Federal Regulations) was issued in 1977 by the U.S. Office of theSecretary of Defense that the day–night average sound level DNL must be usedas the basis for evaluating the impact of noise by air installations and that neitherCNR nor NEF may be utilized.In 2002, the European Parliament and Council issued Directive 2002/30/ECon the establishment of rules and procedures with regard to the introduction ofnoise-related operating restrictions at airports. The objectives of this Directive are(a) to lay down rules for the Community to facilitate the introduction of operatingrestrictions in a consistent manner at airport administrative level so as to limit orreduce the number of people significantly affected by the harmful effects of noise,(b) to provide a framework which safeguards internal market requirements, (c) topromote development of airport capacity in harmony with the environment, (d)to facilitate the achievement of specific noise abatement objectives at the levelof individual airports, and (e) to enable measures to be chosen with the aim ofachieving maximum environmental benefit in the most cost-effective manner.13.10 Evaluation of Traffic NoiseHighway traffic noise probably impacts more people than any other source ofoutdoor noise. Consequently, many national, state, and local governments set requirementsto assess the existing or potential noise impact of highways. In theUnited States, federal agencies are required by law to provide environmental impactstatements (EIS) for proposed new roads and for any reconstruction of existing