Time Correction for Leq

Equivalent Continuous Sound Pressure Level ($L_{eq,T}$)

Basically, the amount of acoustic energy that is lasts continuously throughout measurement time, T, and is equivalent to the actual measured fluctuating sound pressure levels.

Time Correction for Leq (Normalisation)

The $L_{eq,T}$ of an event that last for time period, T, could be corrected to another reference time, $T_n$ using the following equation:

\[L_{eq,n} = L_{eq,T} + 10\log(\frac{T}{T_n})\]

Example

Let’s say that we have a measured $L_{eq,5s}$ of a single train passby event that last for 5s is 95 dB(A). We would like to obtain the $L_{eq,1hr}$ to assess against authority requirements. Assuming that each hour there would be 10 train passby event on a single train track. \(L_{eq,1hr} = L_{eq_3600s} = L_{eq,5s} + 10\log(\frac{10(T_5s)}{T_3600s})\)

\[L_{eq,1hr} = 95 + 10\log(\frac{10(5)}{3600})\] \[L_{eq,1hr} = 95 - 18.6\]

\(L_{eq,1hr} = 76.4 \text{ dB(A)}\)

References

[1] “Time Correction” Jun. 02, 2020. Accessed on Sept. 05, 2023. [Online]. Available: https://strutt.arup.com/help/Fundamentals/TimeRatioAtten.htm