CNEL is the California metric used to measure noise annoyances.
The FAA is using the wrong noise metric to describe aircraft noise in the Draft Environmental Assessment (EA). California’s differing cultural and environmental noise threshold expectations are reflected in the State’s mandate to use the Community Noise Equivalent Level (CNEL) metric for assessing airport noise exposure. The FAA is using Day-Night Average Sound Level (DNL). Both metrics add a 10dB penalty to aircraft operations between 10pm and 7am. The CNEL adds an extra 5dB penalty during the 7-10pm evening hours.
The FAA accepts the CNEL as a metric to measure the exposure of individuals to noise resulting from the operation of an airport. Using DNL instead of CNEL in the EA results will result in findings being out of synch with the general public’s expectations and is contrary to California Law.
 CA Department of Transportation, State Aeronautics Act (Public Utilities Code Section 21669), California Code of Regulations (Title 21, Division 2.5, Chapter 6, Section 5000 et seq.).
 Source FAA Order 1050.1E Appendix A, Paragraph 14.1.a., FAA Airports Desk Reference 17.1(c)