i think that it will travel less then that cos it will absorb sound energy
How fast does sound travel through foam?
Are you referring to acoustic foam? That's the type of foam which is primarily used in conjunction with sound. It's designed to reduce wave energy the effectiveness of which is determined through a noise coefficient rating. As mentioned above the rate at which the sound is traveling wouldn't differ much to the speed in which it travels through the air.
Sound travels faster in liquids and non-porous solids than it does in air. But as foam is a porous solid, the speed of sound will be roughly equivalent to the speed of sound in air: "In dry air at 20 °C (68 °F), the speed of sound is 343.2 metres per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph), or about one kilometer in three seconds or approximately one mile in five seconds." -- wiwipedia. So it will be ROUGHLY that speed, as we don't know the temperature and moisture of the air inside the foam :)