If I recall correctly (its been loooong time) the underlying process behind this is quite simple.
Temperature is a measure of the kinetic energy of the motion of the atoms (well, molecules for the gases that comprise air). Kinetic energy is proportional to the square of the velocity of the individual molecules.
E = 1/2 m V*V
Absolute zero is the point at which all motion ceases. This is why temperatures below that cannot exist.
The speed of sound is the result of the average time and distance that a gas molecule travels before bumping into another one. The hotter the gas, the faster the molecules are moving the less time that transpires before a molecule bumps into the next one and the faster the sound pressure wave travels.