Smith finished with 257,020 votes, beating Melton, who finished with 250,554, by just under 7,000 votes. Ndamukong Suh of the Detroit Lions finished third.
Smith is in his 12th season in the league out of Missouri. This year, he has 66 tackles and three sacks in 14 games for a 49ers defense that is ranked first in the league in points allowed per game and second overall in yards allowed per game.
Melton, in his third season out of Texas, has 41 tackles, six sacks and four forced fumbles. Chicago's defense is third in the league in points allowed per game and fifth in yards allowed per game.
Suh, a third-year player out of Nebraska, has 29 tackles and 6.5 sacks for the Lions this season.