110 dB is 60 dB louder than 50 dB.
60 dB means 1 million times the original sound power.
To increase the sound power level in that office by 1 million times, if everyone speaks at the same level, you'd need a million times as many people as you started with.
For every person who's already there, you need to ADD 999,999 MORE people ... into that SAME office !