The Lden indicator (for Level day-evening-night) represents the weighted average noise level during the day. The formula for the calculation of the Lden:

\[ Lden = 10 \log_{10} \left( \frac{1}{24} \left( 12 \times 10^{\frac{LAeq(6h-18h)}{10}} + 4 \times 10^{\frac{LAeq(18h-22h)+5}{10}} + 8 \times 10^{\frac{LAeq(22h-6h)+10}{10}} \right) \right) \]

- LAeq in dBA, the equivalent sound pressure level on a period T