The day-night average sound level (Ldn or DNL) is the average noise level over a 24-hour period. The noise level measurements between the hours of 22:00 and 07:00 are artificially increased by 10 dB before averaging.
The day-night average sound level (Ldn or DNL) reflects the total noise level throughout a 24-hour cycle. Noise levels between 22:00 and 07:00 are elevated by 10 decibels prior to determining the average value.