Answer
By $\frac{1}{4}$
Work Step by Step
The intensity of sound is equal to $$I=\frac{P}{A}=\frac{P}{4\pi R^2}$$ Since $R'=2R$, the new intensity becomes $$I'=\frac{P}{4\pi (2R)^2}=\frac{P}{16\pi R^2}=\frac{1}{4}I$$ This means that the intensity is multiplied by $\frac{1}{4}$.
