Probably very fast indeed if one considers things like nuclear matter or the quark soup expected from the LHC or the material of a neutron star... The sums get a bit difficult though. It'll be a big fraction of the speed of light.
solids
The SR-71 is the fastest manned jet. Its fastest recored speed is Mach 3.3 (3.3 the speed of sound.)
no light is the fastest on earth
sound travels the fastest through a solid perferably dimond.
The Creative Sound Blaster X-Fi is one of the fastest sound cards available.
The fastest is mach 3.3 or 3.3 times the speed of sound. The SR-71 Blackbird can go that fast. There may be faster jets but governments would keep that information classified.
Sound travels the fastest in solids. Solids being the most denser make sound travel fastest as compared to liquids and gases which have speed of sound relatively less than solids.
Sound waves travel the fastest through nonporous solids.
sound travels fastest in cold
Sound travels fastest, and best through a solid. eg. steel
Sound travels fastest in solids, so it would travel fastest in wood compared to air and water.
sound travels fastest in solid (about 8x faster)