Rear suspension noise when going over bumps in road?

2002 Hyundai XG350L with 47,000 miles. Very soft riding car with new Michelins installed 4 months ago. This noise just started a week ago. When going over a bump (most often a raised bump like a pavement blowup) the rear suspension is very noisy and hard riding. When the rear tires drop into a pothole or drop off there is little or no noise. Struts are not leaking. Everything looks good from an initial visual inspection. Car was 4-wheel aligned and the alignment just rechecked. I think I know what it is but I welcome feedback to confirm my suspicion.