The Defense Has Claimed:  The City and County of San Francisco (CCSF) is in full compliance with state noise regulation.
What the law says:
         "The California Airport Noise Standards states that the basis for the
         acceptable level of aircraft noise for persons living in the vicinity of
         airports is a CNEL of 65 decibels. It's the noise standard that defines
         the airport's noise contour and is recognized by the FAA as the
         federal standard."
         People in Burlingame, Hillsborough, San Mateo, and most of
         Millbrae do not live in the airport's noise contour.
         See noise contour map below.

Below is what a “CNEL” measurement (what the airport uses) would look like. Each of these 3 days would show a noise equivalent of 65 A-weighted decibels, an acceptable level from the airport’s view.


Source: Informal Hearing Brief of Defendant, 2019, page 10.
If 100 aircraft a day flew to/from SFO, it would satisfy the California Airport Noise Standards that the City and County of San Francisco maintains it complies with.

As of December 31, 2018, airport operations averaged 1287 a day, more than 10 times what is acceptable to the California Airport Noise Standards.

Additionally, CNEL measurement does not apply to where we live and what we hear.