What is CNEL? A plain-English guide

Updated 23 October 2026

Modeled estimates for general information only — not measurements, not a guarantee, and not for legal, medical or real-estate decisions.

CNEL, the Community Noise Equivalent Level, is a 24-hour average sound level in decibels used in California. Evening sound (7 to 10 pm) counts 5 dB heavier and night sound (10 pm to 7 am) 10 dB heavier than day. DNL, also written Ldn, has no evening addition, and Caltrans puts CNEL about 0.5 dB above it for the same sound.

See the 24 h CNEL view near LAX

How is CNEL worked out?

CNEL takes the sound level of each of the 24 hours of a day, adds a penalty to the evening and night hours because noise is harder to ignore then, and averages the result as energy. Caltrans’ Technical Noise Supplement writes the evening penalty as 10 log 3, which is 4.77 dB and is commonly rounded to 5, and the night penalty as 10 dB.

These are the periods of the map’s Day, Evening and Night buttons. The 24 h button is CNEL.

What is the difference between CNEL, DNL and Ldn?

The state’s General Plan Guidelines call Ldn a simplification of CNEL with no significant loss in accuracy, and say noise elements use either. For one sound, Caltrans says CNEL is normally about 0.5 dB higher than Ldn using the same 24-hour data. For the decibel scale itself, see what 45, 55 and 65 dB mean.

One inconsistency in Caltrans’ supplement is worth knowing: its prose on Ldn gives the night hours as 10 pm to 6 am, while its table, equation and CNEL glossary use 10 pm to 7 am. Quiet LA uses 10 pm to 7 am, as the table, the equation, the glossary, the state’s guidelines and the CNEL regulation do.

What does 65 CNEL mean?

65 is the level airport rules are built around, and it is a planning number for land use near airports, not a line for a home. California’s airport noise standard, Title 21 section 5012, sets the acceptable aircraft noise level for people living near airports at a CNEL of 65 decibels, and it bars a “noise problem airport” from operating with a noise impact area based on that standard unless it has applied for or received a variance.

Federally, the FAA says it designated the DNL 65 contour as the level above which residential land uses are not compatible. In 14 CFR Part 150, Appendix A, all land uses are considered compatible with noise levels below Ldn 65 for the purposes of that part. Airport noise exposure maps show contours at 65, 70 and 75, and Table 1 says responsibility for acceptable land uses rests with local authorities. These are airport planning rules for a yearly average of aircraft noise. They are not a statement about any address, and Quiet LA never says a place meets or fails a standard. For what 65 dB sounds like in everyday terms, see how loud is 65 dB.

How does the Quiet LA map use CNEL?

The map’s 24 h view is CNEL: road and train noise, plus the aircraft estimate when the Aircraft switch is on. The aircraft estimate is derived from each airport’s official contours, stretched outward to 55 CNEL; the map draws airport lines in steps from 55 CNEL up. Day, Evening and Night never include aircraft. The values are modeled estimates, typically about 6 dB off at one spot. See LAX and aircraft noise and airport noise in Los Angeles County.

You cannot compare the map to an official CNEL contour as if they were the same thing. The official contours come from an airport’s own reports and use its flight data; Quiet LA’s aircraft level is an estimate from them, in the 24 h view only, and it is not an official level.

The map’s method is on How it’s made and Sources & methods, and its limits on Limits.