My daughter figured out a way to make my table much quieter. She first noticed that the sisbot (if that's the right term) made no noise at all when disconnected from the table. However, she could feel it vibrating. So she figured the problem was the transference of that vibration to the table. The table itself then acts like a drum and amplifies the sound. Next, she cut eight octagonal rubber washers out of a wide rubber band. She added two to each of the four screw-fasteners (also, pictured below). The octagonal shape made it easier to position the washers. Finally, she did not tighten the screws all the way, and thus the metal part of the sisbot does not come up to touch the braces. (She experimented with putting washers on both sides of the sisbot plate, but that did not work as well.) At this point, the only noise we get is from the ball rolling through the sand. My table is *much* quieter now. She also has ideas for alternative ways of dampening the vibration.
I'm very noise conscious myself. Can you tell me what speed you have your slider set at (if you have connected and changed the default speed)? Does it make sound when it's not moving (but still plugged in)? Thank you for describing the sound: whirring. That is very helpful! This is an ongoing hunt to make our system work as quietly as possible.