I am assuming you know the Chinese balls routine. The small metal balls that have bells within. You can work on lots of stuff with them. For one you can do the original rolling in the hand having them not touch and make no sound. You can hold them and rotate them with the hand to the side or backwards and it is fun to do. Check what direction is easier to rotate the balls as your palm faces the floor. Anther way is to throw and catch them trying to make no sound. From the back and over the shoulder works nicely and helps in working or a good punch. As in all work. Noise is a tell you are doing something wrong (Well almost any work 🙂 ) Try to make no sound as you walk, sit and do anything in daily life. Practice and enjoy your progress and understand why we sometimes fail.