Imagine holding on to a large, metal pipe (like a hand rail on stairs) and someone on the other end, hitting the pipe with their hand, not a big “clung”, but like they swung past it, and barely nicked the pipe with the tips of their fingers as their arm swung by. Combine that vibration with a breathy, hollowness that kinda warbles as the rubber ball contracts and expands due to the impact. The whole sound only lasts about a second - unless you were the one that got hit in the head, in which case there’s a high pitched ringing in your ears for a bit as well.