By definition, sound intensity, I, in terms of decibels is
[tex]I_{db} =10 \,log( \frac{I}{I_{0}} )[/tex]
where
I₀ = reference intensity.
With two sound sources,
[tex]10 \, log( \frac{2I}{I_{0}} ) = 86 \\ log( \frac{2I}{I_{0}} ) = 8.6 \\ \frac{2I}{I_{0}} =e^{8.6} \\ \frac{I}{I_{0}} =e^{8.6}/2 = 2715.83[/tex]
Therefore with one sound source, the decibel level is
[tex]10 \, log( \frac{I}{I_{0}} ) = 10 \, log(2715.83) = 34.34 \, db[/tex]
Answer: 34.3 db
