Before reading the questions:
- The ball was uniformly gray, with a slight shine.
- The person was genderless and featureless. I only pictured their hand and arm pushing the ball. The moment of contact was indistinct, as if the arm was hiding the ball from view.
- The ball was the size of a large watermelon.
- The table was square, about 1m² , brown-gray, with four turned legs. Same material as the ball: uniformly colored and vaguely glossy.
Sounds just like the sounds newer trucks make when they back up: https://m.youtube.com/watch?v=A3Wt1_51EVA