Equivalent sound level

Professional Definition

Equivalent sound level (denoted as Leq or LAeq,T) is a constant sound level that, over a specified period of time (T), carries the same acoustic energy as the actual sound with avariable level.

In acoustic engineering, this is a fundamental measure of noise dosage. It is important to understand that it is not the arithmetic mean of decibels, but the energy mean. Due to the logarithmic nature of the decibel scale, short-term events with very high levels (e.g., an airplane flyover) have a dominant effect on the final Leq result compared to a long-term acoustic background.

Acoustics in Simple Words

Imagine noise as a terrain - we have high mountains (loud, sudden sounds) and valleys (moments of silence). The equivalent sound level is the action of a bulldozer that flattens the mountain peaks and fills the valleys, creating a perfectly flat area. The height of this flat terrain is the Leq. It shows how loud it would be if all the noise energy from a given period (e.g., 8 hours of work) were distributed evenly, without any interruptions and jumps.

Summary

The equivalent sound level is the most important parameter used to assess long-term noise exposure. It allows for the comparison of various acoustic environments by reducing time-varying sounds to a single, averaged energy value, which is essential when designing noise barrier protections.