In the movie Sully they watch the flight simulations and they can hear the audio on the whole room.
But when switch to the black box recording everyone needs to use headphones.
So why they dont simply use the same audio system as the one for the simulation.
I cant imagine how complicated was put a headphone for each person and setup a plug for each headphone.
In addition to Paulie_D's answer which is logically correct that the subset of people needed to hear it clearly. I am trying to answer the why ?
As this was a hearing in procession, people sitting in back might be aviation journalist and they might not be privileged to hear the CVR (Cockpit Voice Recording) at that point during hearing.
They however might be privy to proceedings of the hearing hence they are present in room.
CVR's are publicly released after the hearing.
Actually, if you look carefully, it's not the whole room using headsets, just a relatively small subset of people at the tables at the front. The observers at the back are not using headsets.
As such there are, it seems to me a couple of possibilities.
Firstly, that only this subset needed to hear the recording closely enough to require headsets for clarity and that the others had the audio played out loud like the simulations, or
Secondly, the observers at the rear didn't hear the audio at all.
Of the two, the first seems more likely.
There is one other option related to the second in that listening to the cockpit voice recorder could be intensely distressing and so listening to it via headset was optional.
