The ornamental design for a soundabsorbingpanel, as shown and described.
FIG. 1 is a front perspective view of a sound absorbing panel showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right-hand-side elevation view thereof (the left-hand-side elevation view, being a mirror image of the right-hand-side elevation view, is not shown); and,
FIG. 4 is a top plan view thereof (the bottom plan view, being a mirror image of the top plan view, is not shown).