Sharp noise from back wheelhouse when driving over speed bumps

Grateful for any insight. My Toyota Auris Estate 2017 started giving off a sharp noise when driving over bigger speed bumps, same noise appears while testing the suspension while stationary. Investigated the wheelhouse from the outside, everything looks normal. However, I don’t know if it’s related, but found some fibers, maybe nylon, next to the brake pads. Any idea what it might be?