The main feature of Soundball is a continuous sound, which is emitted by special sensors and electric motors. As soon as the ball rolls back and stops, they start making loud noises. It can be found at any time in the match, even during a complete stop.
Blind athletes played with a ball with mechanical "rattles" inside, which can be heard during active play. As soon as it rolled somewhere on the field, the game stopped. Blind players simply could not find such a ball.