we can use
sound level formula
[tex]\beta=10log(\frac{I}{I_0} )dB[/tex]
where
[tex]\beta[/tex] is the sound level for a noise
I is intensity given
I0 is reference intensity
we know that reference intensity as
[tex]I_0=1*10^{-12}W/m^2[/tex]
we are given
[tex]I=9.9*10^{-5}W/m^2[/tex]
now, we can plug these values
and we get
[tex]\beta=10log(\frac{9.9*10^{-5}W/m^2}{1*10^{-12}W/m^2} )dB[/tex]
now, we can simplify it
[tex]\beta=10log(9.9*10^{-5+12} )dB[/tex]
[tex]\beta=79.95635dB[/tex]................Answer