  This paper is concerned with a viscoelastic equation of Kirchhoff type with
acoustic boundary conditions in a bounded domain of $\mathbb{R}^{n}.$ We show
that, under suitable conditions on the initial data, the solution exists
globally in time. Then, we prove the general energy decay of global solutions
by applying a lemma of P. Martinez, wihch allows us to get our decay result for
a class of relaxation functions wider than that usually used.
