Different materials will act and behave differently when they are implemented to sound. It isn't always the materials that will change due to sound but some what the sound has a greater risk of changing due to the effect of the material.

As sound is a vibration it has the ability to travel through liquids, solids and gases. Different materials will have a greater effect on sound and will give different results i.e. metal is great for sound to travel through and will amplify and make the sound louder where as rubber is a solid but it is a dampner on sound and will make the sound quieter and muffled. The only time sound will not travel is through a vacuum. Wood doesn't really effect how sound sounds or travels and this is proven hence the reason so many speaker housing units are made from it. Cloth or fabric has absolutely no affect on sound unless the cloth is really thick, we know that it doest affect sound greatly as it is used to cover speaker fronts on most speaker systems around today.