GOALBALL has been part of the Summer Paralympics since 1976. At the London 2012 Paralympics, 72 men and 60 women will be competing in 12 men's and 10 women's teams at the Copper Box venue in Olympic Park from August 30 through September 7. Goalball is played by visually impaired athletes, and all players wear eyeshades to equalize various degrees of impairment. There are two events, one for men and one for women.
According to the description on the site of the International Paralympic Committee, "The object of the game is to roll the ball into the opposite goal while opposing players try to block the ball with their bodies. Bells inside the balls help orient the players, indicating the direction of the on-coming ball. Therefore, while play is in progress, complete silence is required in the venue to allow the players to instantly react to the ball."
You can read more about Paralympic Goalball on the site of the International Blind Sports Federation.