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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>AIRPORT NOISE CLASSIFICATION</title>
      <link>https://trid.trb.org/View/52692</link>
      <description><![CDATA[The use of A-weighted noise spectrum has gained widespread acceptance.  The A-weighting produces a measure of the loudness of a sound as opposed to the annoyance measured by PNL (Perceived Noise Level).  Following a background information on the acoustical concepts of loudness and noisiness, the paper describes four airport noise classification systems referred to as CNR (Composite Noise Rating), NEF (Noise Exposure Forecast), Ldn (Day-Night Level), and ASDS (Aircraft Sound Description System).  The CNR system is based on PNL as the fundamental measure of annoyance, while NEF uses effective PNL as the basic noise unit.  The two A-weighted systems, Ldn and ASDS, are developed in an attempt to simplify the concepts involved in noise classification, and yet maintain a reasonably objective and effective system.  The salient features of the comparisons made is that there are really only minor differences in these various approaches to airport noise classification.  These differences are mainly the result of rather arbitrary determination of the relative effect of daytime as compared to nighttime operations.]]></description>
      <pubDate>Wed, 28 Sep 1977 00:00:00 GMT</pubDate>
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      <title>REPORTS OF SLEEP INTERFERENCE AND ANNOYANCE BY AIRCRAFT NOISE</title>
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      <description><![CDATA[The paper presents the results of a community noise survey in which 1500 residents living in 11 communities near Kennedy Airport in New York were interviewed with regard to their night, day, and evening annoyance responses to aircraft noise.  It was found that, while nighttime operations are only 35% of evening a 48% of daytime activity, the reported mean annoyance during the night is 71% of evening and 90% of the daytime reported annoyance. This suggests that each nighttime flight has the equivalent annoyance effect of 2 day on evening flights.  This is compared with the ENR, NEF and Ldn indexes that assume that 10 daytime flights are the equivalent of one nighttime flyover.]]></description>
      <pubDate>Tue, 20 Sep 1977 00:00:00 GMT</pubDate>
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