It's the venerable custom in tennis and golf for the crowd to be still and quiet when players hit their shots.
Now, since even ordinary baseball batters have some success hitting against 98 mph fastballs with 40,000 fans standing and screaming, do you really believe that great athletes like Novak Djokovic or Rory McIlroy couldn't serve or putt with a few thousand fans hollering? If they'd grown up playing tennis or golf that way, that is. When disorder is a sustaining part of the game, players, in effect, put it out of their minds. Hear no evil, see no evil.