A person is talking in a small room and the sound intensity level is 60 dB everywhere within the room. If there are eight people talking simultaneously in the room, what is the sound intensity level?

Let intensity due to a single person = I
then 10 $\log \frac{\mathrm{I}}{{\mathrm{I}}_0}$ = 60
Also, Intensity due to 8 person = 8I
$\therefore$ Final decibel level

= $10\log \left(\frac{8\mathrm{I}}{{\mathrm{I}}_0}\right) = 10(\log \frac{\mathrm{I}}{{\mathrm{I}}_0}+\log 8)$

= 60 + 10 log 8 = 60+30 log 2 = 60+30(.3010)

= 69 dB