Answer
$I \approx 6.31 * 10^{-3} \frac{W}{m^2}$
Work Step by Step
Given the decibel equation $B = 10 \log \frac{I}{I_{0}}$
with $I_{0} = 10^{-12} \frac{W}{m^2}$
Given the decibel level of a subway train at $B = 98 dB$
Find the sound intensity
$98 = 10 \log \frac{I}{10^{-12}}$
$9.8 = \log \frac{I}{10^{-12}}$
$10^9.8 = \frac{I}{10^{-12}}$
$I = 10^{-2.2} \frac{W}{m^2}$
$I \approx 6.31 * 10^{-3} \frac{W}{m^2}$
