Day-Night Average Sound Level
Encyclopedia
The Day-Night Average Sound Level (Ldn or DNL) is the average noise level over a 24 hour period. The noise between the hours of 10pm and 7am is artificially increased by 10 dB
. This noise is weighted to take into account the decrease in community background noise of 10dB during this period.
The Federal Aviation Administration
has established this measure as a community noise exposure metric
to aid airport noise analyses under Federal Aviation Regulation Part 150.
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
. This noise is weighted to take into account the decrease in community background noise of 10dB during this period.
The Federal Aviation Administration
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
has established this measure as a community noise exposure metric
Noise measurement
Noise measurement is carried out in various fields.In acoustics, it can be for the purpose of measuring environmental noise, or part of a test procedure using white noise, or some other specialised form of test signal....
to aid airport noise analyses under Federal Aviation Regulation Part 150.