When you move your hand with a slinky in it, the slinky begins to move because you gave energy from your hand to the slinky. A wave is not always formed, but when the disturbance from your hand is rhythmic, a wave will form. Is this right so far? A force acted on the slinky and caused a disturbance. Gravity is a force that acts on all objects with mass including air molecules. Therefore why does gravity not create a disturbance on air molecules and cause sound or movement as in a wave?