Essentially speaking, sound is a type of vibration which only transmits through a sort of a medium and which is in RP created by combination of lighting and wind element. Now, keeping this in mind, the movement of sound would solely depend on the physical properties within which medium sound is moving forth. The movement of sound, or vibrations would depend on the density of the medium, on the movement (if it is going in the same direction or going against it) and on the viscosity (the less viscous the fluid/medium is, the easier would be the movement of the vibrations due to the lack of resistance.) . Sound would travel faster in liquids and non-porous solids than it would in the air. The sound element in the RP would be weak only against things which can disrupt the medium through which it is moving, hence why it is weak against the element of wind. In some cases however it can be weak against earth element, but that would apply to only sound waves which have destructive properties rather than ones with hindering or genjutsu traits. On the other hand, elements which have constant physical properties, especially solid ones, will easily get shuttered by sound.