What is Day-Night Sound Level?
Day-Night Sound Level (DNL) is a way to measure the relative intensity of sound, or decibels, over a typical 24-hour day averaged over the course of a year. The higher the number, the louder the sound received by the human ear. Because people are generally more sensitive to noise at night (ambient noise levels are usually lower), night-time noise measurements are more heavily weighted in the calculation of DNL. DNL measurements may be expressed for individual locations or expressed in noise contours, like the contours of elevation in a topographical map. Noise monitors can be used to capture when the noise event happened and records its measurements but modeling noise events using DNL give us the ability to consider the sensitivity of the noise to the listener.
