Answer
The loudness of this sound level is 130 decibels.
Work Step by Step
The intensity of sound from the race car is about $10\text{ W/}{{\text{m}}^{\text{2}}}$.
Thus, $I=10$.
Substitute $I=10$ and ${{I}_{0}}={{10}^{-12}}$ in the formula $L=10\cdot \log \frac{I}{{{I}_{\left( 0 \right)}}}$ and solve as follows:
$\begin{align}
& L=10\cdot \log \frac{I}{{{I}_{\left( 0 \right)}}} \\
& L=10\cdot \log \frac{10}{{{10}^{-12}}} \\
& L=10\cdot \log {{10}^{13}} \\
\end{align}$
Now convert it into an exponential equation by using the formula ${{\log }_{a}}x=m\rightarrow{{a}^{m}}=x$:
$\begin{align}
& L=10\cdot \log {{10}^{13}} \\
& L=10\cdot 13\log 10 \\
\end{align}$
$\begin{align}
& L=10\cdot 13\log 10 \\
& L=10\cdot 13\cdot 1 \\
& L=130 \\
\end{align}$
