. By assuming the minimal conditions on the relaxation function g: g′(t) ≤ ξ(t)G(g(t)), where G is a convex function, we establish optimal explicit and general energy decay results to the system. Our result holds for G(t) � tp with the range p ∈ [1, 2), which improves earlier decay results with the range p ∈ [1, 3/2). At last, we give some numerical illustrations and related comparisons.