CNEL (Community Noise Equivalent Level)

What is CNEL and how is it used?

CNEL is the acronym for Community Noise Equivalent Level.

CNEL is a single number result that is calculated for a complete 24-hour period and usually made up of results taken at shorter intervals such as 5 minutes or 1 hour and then averaged over the whole 24 hours. 

CNEL is the average sound level over a 24 hour period, with a penalty of 5 dB added between 7 pm and 10 pm. and a penalty of 10 dB added for the nighttime hours of 10 pm to 7 am.

The logic behind these applied penalties is that since most citizens living in a given area are very sensitive to noise in the early morning hours and somewhat sensitive to noise during evening hours, a weighting factor is applied. 

CNEL depends not only on the noise level of individual aircraft approaches, but also on the number of aircraft approaches during the measurement period.

Impacts of CNEL are both actual and perceived for noise in specific localities around airports.  Contour lines are used when depicting existing CNEL noise exposure. 

Williams Aviation Consultants Inc. has a working knowledge and experience in evaluating the impacts of CNEL in Environmental Impact Statements and Environmental Assessments and has helped our clients understand the noise impacts affecting their community’s environment.