# Strength

Sound strength, G, represents the logarithmic ratio of this sound energy to that of the response measured in a free field at 10 m distance from the sound source. 

${G}$ can be calculated according to the following equation, where $t = 0$ corresponds to the start of the direct sound, and $\infty$ to a time that is greater than or equal to the point at which the decay curve has decreased by 30 dB.

${G} =10 \lg \frac{\int_{0}^{\infty}h^{2}(t)\mathrm{d}t}{\int_{t_e}^{\infty}h_{10}^{2}(t)\mathrm{d}t} = L_{p_E} - L_{p_E, 10} \mathrm{dB}$

The terms $L_{pE}$ and $L_{pE,10}$ can be expressed as:

$L_{pE} = 10 \lg \left [ \frac{1}{T_0} \int_{0}^{\infty}\frac{h^{2}(t)\mathrm{d}t}{p_0^{2}} \right ] \mathrm{dB}$

and

$L_{pE,10} = 10 \lg \left [ \frac{1}{T_0} \int_{0}^{\infty}\frac{h_{10}^{2}(t)\mathrm{d}t}{p_0^{2}} \right ] \mathrm{dB}$

where

$h(t)$ is the impulse response measured at the measurement point;

$h_{10}(t)$ is the impulse response measured at a distance of 10 m in a free field,

$p_0$ is 20 µPa;

$T_{0}$ = 1 s

$L_pE$ is the sound pressure exposure level of $p(t)$;

$L_{pE,10}$ is the sound pressure exposure level of $p_{10}(t)$.

 ISO 3382-1:2009 Acoustics — Measurement of room acoustic parameters — Part 1: Performance spaces.