At the beginning of the movie First Man (2018) there was a message displayed to the audience warning about some firework noises which were an intended part of the movie and not to be alarmed. I was slightly distracted and didn't catch the full message or if it gave any further explanation.
At the point of the movie right after Neil Armstrong and Buzz Aldrin land on the moon and are sitting in the cockpit, there were indeed audible popping noises which sounded like there were fireworks going off outside the theater.
What were those noises? Did the message at the beginning explain it more or is there some kind of explanation from the actual accounts from Armstrong or Aldrin?