Answer
$-230$ decibels
Work Step by Step
We have $\beta=10 \log (II_0)$
Plug in the data:
Therefore, $\beta=10 \log (10^{-12} \times 10^{-11})= 10 \log 10^{-23}$
Or, $\beta = 10 (-23) \log 10 =-230$
Therefore, the sound level is $\beta = -230$ decibels