Sometimes, domes can be loud. Like VERY LOUD. So loud that you can't yell "Hey, come back! Come back!" to your running back who is lined up on the wrong side of the formation.
Such was the case in New Orleans early in the first quarter when Niners quarterback Colin Kaepernick and fullback Bruce Miller was trying to get Frank Gore's attention, as he broke out to the wrong side of the formation.
So, what do you do when your teammate can't hear you scream? YOU CLAP LIKE A MADMAN.
That didn't work either, so the Niners had to burn a timeout. Better clap harder next time, guys, or ask Saints fans to quieten down a little bit.