Lden stands for Day-Evening-Night noise Level.
Lden is the European standard used in all noise studies, so it’s worth understanding — and since today, April 29th, is International Noise Awareness Day, we thought it was a good moment to get to know it better.
We already know that noise affects our hearing and that it’s a social problem still waiting to be addressed, both by governments and through education, especially for younger generations who are highly exposed to the entertainment industry and headphone use.
The most widely used international measurement for noise is Decibels (dB), which help us measure the intensity of a noise at a given moment. But when we want to measure how much noise the population is exposed to, knowing the noise level at one specific moment isn’t enough — we need to know exposure over 24 hours or across different times of day.
Leq: Equivalent Continuous Noise Level
Leq, the Equivalent Continuous Noise Level, does exactly this: it’s a measure of the energy equivalence of all the noise energy produced over a given period, making it easier to compare noise exposure across different environments.
Lden is a measure derived from Leq, and it’s the indicator proposed for measuring noise by European Directive 2002/49/EC of 25 June 2002, relating to the assessment and management of environmental noise.
Lden Time Periods and Adjustments
Lden is made up of three time periods, each with its own adjustment in dB
| Period | Hours | dB adjustment |
|---|---|---|
| Day | 7 – 19 | 0 dB |
| Evening | 19 – 23 | 5 dB |
| Night | 23 – 7 | 10 dB |
Ld, Le and Ln
Besides Lden, there are other units of measurement for different times of day.
| Unit of measurement | Description |
|---|---|
| Lden | European standard for average noise level across day, evening and night, applying a 10 dB penalty to night-time noise between 11pm and 7am, and a 5 dB penalty to evening noise between 7pm and 11pm. |
| Ld | Average daytime noise level, from 7am to 7pm. |
| Le | Average evening noise level, from 7pm to 11pm. |
| Ln | Average night-time noise level, from 11pm to 7am. |
Lden Calculation Formula
This is the formula used under European regulations to calculate Lden:
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