Explanation:
When the sound intensity level is \(60\;dB\),
\(10\log \left( {\frac{{{I_{60}}}}{{{I_0}}}} \right) = 60 \Rightarrow {I_{60}} = {10^6}{I_0}\),
where \({I_0} = \) reference intensity.
Similarly for \(30\;dB,{I_{30}} = {10^3}{I_0}\)
Hence \(\dfrac{I_{60}}{I_{30}}=1000\).