Wyle Labs., 2001 Jefferson Davis Hwy., Ste. 701, Arlington, VA 22202
A wide variety of metrics are available to represent and evaluate noise impacts from aircraft operations. Two of these have gained wide acceptance and are used extensively in noise studies and mitigation programs throughout the United States: Day night average sound level (DNL) and sound exposure level (SEL). A third metric, time above (TA), is not often used but is very often requested by community members who believe it will represent their noise problem more convincingly than the others. Each metric differs significantly from the others both in the way it represents noise impact and in way the measure is best employed. For example, since DNL accounts for the loudness of individual events and the number of operations, an equivalent DNL value can result from a few very loud overflights or a large number of quieter ones. DNL is considered useful in predicting the average response of communities but not of individuals. The authors evaluated the noise impact for different sized airports (based on number of operations) by examining each of the three metrics DNL, SEL, and TA. The noise impacts are compared and the best use of the information is discussed.