AFAIK, NFHS only has verbal obstruction in the rulebook, However, under 10-1-1, "Any umpire has the authority to order a player, coach or team attendant to do or refrain from doing anything that affects the administration of these rules and to enforce prescribed penalties." This means that if an umpire judges that the catcher knocking the ball against the ball to confuse the offense, the umpire can order the catcher and his team to refrain from doing that. If the catcher refuses to comply, he can be ejected, and obstruction can be enforced ("Obstruction is an act... by any member of the defensive team that hinders a runner or changes the pattern of play", and throwing the ball against a bat to simulate a hit changes the pattern of play). Thus, both your example and the OP can legitimately be considered obstruction, because the runners in the example might hear the sound and believe that the ball was hit, and the batter might also run because the ball was hit. In this case, the umpires would shut the play down to prevent unnecessary confusion, and warn the defensive team or eject the catcher for causing confusion in the game, according to 10-1-1. In a minor league game, a catcher threw a potato to third base, and tagged the runner with the real ball. The umpires ruled that the player was not out due to the catcher's actions, and awarded him home. Therefore, if using a potato to mislead a runner is obstruction, then throwing the ball against the bat to simulate a hit is also obstruction.