This study aims to examine the existing single rating index in terms of level reduction limit of heavy-weight floor impact sound. To achieve this goal, sounds which have same loudness according to rating methods were suggested to subjects. And followings are results. 1) The rating method of measurement frequency level average is more suitable than that of other methods which are dependent on specific frequency for rating heavy-weight floor impact sound. 2) Level average for measurement frequency of $31.5;Hz{sim}500;Hz$ is more correspondent to psycho-acoustic response than that of measurement frequency of $63;Hz{sim}500;Hz$ which is for KS F 2863-2, existing rating method.