Answer
The sound level is $~~39.5~dB$
Work Step by Step
In part (a), we found that $I = 8.84\times 10^{-9}~W/m^2$
We can find the sound level in decibels:
$\beta = (10~dB)~log(\frac{I}{I_0})$
$\beta = (10~dB)~log(\frac{8.84\times 10^{-9}~W/m^2}{10^{-12}~W/m^2})$
$\beta = 39.5~dB$
The sound level is $~~39.5~dB$
