In tennis, I believe the fans have to be completely silent while the ball is in play. The umpire would have to ask them to if the players are ready to play and there's still noises. Even when there's some amazing rallies the fans still have to hold their breath until the point is over to applause. I wonder why there's no such rule in badminton. Don't players need to be focus too when the shuttle is in play? Wouldn't they be distracted when people making some 'feeling-exciting' noise when they're about to have a smash?