What does DNL stand for in aviation noise measurement?

• A. Day-Night Average Sound Level
• B. Daily Noise Level
• C. Decibel Normalized Level
• D. Dynamic Noise Level

Answer: (A)

DNL stands for Day-Night Average Sound Level, a 24-hour aviation noise metric that weights nighttime noise more heavily to reflect greater disturbance during those hours. It averages all sound levels over a day but adds a 10 dB penalty to the nighttime period (typically 10 p.m. to 7 a.m.) before averaging. The result is expressed in decibels and is used to assess environmental impact around airports and to compare noise environments over time. The other terms listed aren’t standard measures in aviation noise measurement, which is why DNL is the correct recognized abbreviation.