Thanks for the Sansa Clip suggestion. It looks like I'll definitely have to buy a compatible device to listen to audible books because audible will not play on just any MP3 player. They're as protectionist and anti-competitive as Australian publishers.
No rock is completely impermeable, but some porous rocks like shale and pumice are mostly impermeable, because the pores are not interconnected, thus not allowing fluids or gases to pass through them. This is why shale makes a good cap-rock, and pumice floats instead of sinking.
Something that is permeable can be passed through, especially by liquids or gases. I wish I hadn't worn my permeable sweater to the picnic when the weatherman called for thunderstorms. A permeable surface allows materials like liquids to pass through â either in or out. Inside the body, the walls of cells are permeable membranes that allow fluids and nutrients to get in and nourish the cells. A permeable shirt is good to wear in the summer, because it helps release the sweat sticking to the skin.