Day-night average sound level
= Day-night average sound level
{wiki=Day-night_average_sound_level}
The Day-Night Average Sound Level (Ldn or DNL) is a noise metric used primarily to assess the impact of environmental noise, particularly in urban areas and near transportation facilities like airports and highways. It is a 24-hour average sound level that accounts for both the daytime and nighttime noise levels, with a weighting factor that penalizes nighttime noise.