Ln,w + Ci describes how easily impact sound travels through a wall or floor. Impact sound is generated by sources such as dryers, washing machines and heeled shoes on a wooden or tiled floor.
Unlike Rw values, better performing walls or floors have lower values. Therefore when specified, Ln,w + Ci values are maximums while Rw values are minimums. For example, the BCA requires some floors to have Ln,w + Ci < 62.