$\beta =10\log \frac{I}{{{I}_{{}^\circ }}}\Rightarrow \left\{ \begin{matrix} P:\beta =50dB\Rightarrow \log \frac{{{I}_{P}}}{{{I}_{{}^\circ }}}=5\Rightarrow \frac {{{I}_{P}}}{{{I}_{{}^\circ }}}={{10}^{5}}\Rightarrow {{I}_{P}}={{10}^{-7}}\frac{W}{{{m}^ {2}}}  \\ Q:\beta =56dB\Rightarrow \log \frac{{{I}_{Q}}}{{{I}_{{}^\circ }}}=5/6=5+2\times 0/3=5+2\log 2=\log ({{10}^{5}}\times 4)\Rightarrow {{I}_{Q}}=4\times {{10}^{-7}}\frac {W}{{{m}^{2}}}  \\ \end{matrix} \right.$ $I=\frac{\overline{P}}{A}=\frac{E}{A.\Delta t}\Rightarrow E=IA\Delta t$ ${{E}_{Q}}-{{E}_{P}}=(4\times {{10}^{-7}}-{{10}^{-7}})\times 600\times {{10}^{-4}}\times 600=3\times 36\times {{10}^{-7}}J=10/8\mu J$