Day–evening–night noise level

The day–evening–night noise level or L_den is a 2002 European standard to express noise level over an entire day. It imposes a penalty on sound levels during evening and night^[1] and it is primarily used for noise assessments of airports, busy main roads, main railway lines and in cities over 100,000 residents.^[2][3][4] The penalty for sound production during evenings and nights is due to higher nuisance perception during quieter hours and to prevent sleep deprivation for nearby residents.

Examples of several Lden levels around Marseille Provence Airport

Lden 50 dB Lden 55 dB Lden 65 dB Lden 70 dB

Definition

L_den is calculated as:^[5]

${\displaystyle L_{\mathrm {den} }=10\cdot \log _{10}\left({\frac {1}{24}}\left(12\cdot 10^{\frac {L_{\mathrm {day} }}{10}}+4\cdot 10^{\frac {L_{\mathrm {evening} }+5}{10}}+8\cdot 10^{\frac {L_{\mathrm {night} }+10}{10}}\right)\right)}$

Where the long-term average noise levels are defined as:

Part of the day	hours	penalty (dB)
day	07:00 - 19:00	0
evening	19:00 - 23:00	5
night	23:00 - 07:00	10

The exact hours of the three periods may be chosen differently by individual EU member states.

The formula for L_den can be considered a weighted average of the yearly individual noise level during day, evening and night.

See also

• Environmental noise directive
• Day-night average sound level, the US equivalent