As part of the FAA Reauthorization Act of 2018, Congress directed an evaluation of alternative metrics. Various noise metrics have been developed over several decades of research to inform federal policies. The report states that no single metric can cover all situations due to the dynamic acoustical and operational characteristics of aviation noise. The appropriate use of noise modeling and noise measurement are also be reviewed and the context in which each are applicable.

The report concludes that no single noise metric can cover all situations. However, the DNL metric, and similar versions such as Lden, are being used world-wide to assess aircraft noise effects on communities. The report reaffirms the DNL metric as the FAA’s decision-making metric, and states that other supplementary metrics can be used to support further disclosure and aid in the public understanding of community noise effects.

FAA Study regarding day-night average sound levels