Luke 18:39 (NIV)
But he shouted all the more, "Son of David, have mercy on me!"
Sometimes one may have to shout to get God's attention. That's not because God can't hear us and doesn't want to answer our prayers. But that's because we need to know our spiritual poverty and desperation. A desperate man will shout, have himself lowered through the roof (Mark 2:4) to beat the crowd, and risk the crowd's wrath (Luke 18:39) to get the Lord's attention. The subsequent encounter with Christ is fantastic. When Bartimaeus begs the Lord to help Him see, the Lord tells Him, "Your faith has healed you." Notice that Christ didn't say, "I have healed you." Instead, it was the man's faith in God that healed him.
So the next time you want God's attention, defy the crowd and shout!