\textbf{170.} Two people are at distances $d_1$ and $d_2$ from a sound source. A person who is at distance $d_1$ hears the sound 18 decibels louder. $\log 2 = 0.3$. Which of the following is $\dfrac{d_2}{d_1}$? (Assume no energy is absorbed by the medium.)
\begin{center}
(1) $4$ \hspace{2cm} (2) $8$ \hspace{2cm} (3) $9$ \hspace{2cm} (4) $16$
\end{center}