What kind of relationship exists between sound and the temperature of material?

When someone is speaking to you, you are able to hear them because of the sound of their voice. The sound is made possible by the vibration of vocal cords which then travels from the point of origin to your ear, and is then interpreted by your brain. This transmission is possible because of vibration of molecules in the air. That is, sound is basically vibrations traveling in a given medium.

Since sound is the vibration of atoms, it is a form of kinetic energy. Kinetic energy is affected by heat. The more heat a medium has, the higher the kinetic energy of the molecules in that medium. The lower the heat of the system, the lower the kinetic energy. Kinetic energy is related to the observable we know as temperature - or the measure of the movement of heat. Hence, at higher temperature, there is higher kinetic energy, which translates to faster vibrations in the medium, and hence, sound being able to propagate faster though that medium.

At 45C the speed of sound is about 358 m/s, while at lower temperatures of -1C, it's at 330 m/s. 

---in brief,

Since sound is a form of kinetic energy - vibration of atoms/molecules - it is affected by temperature in a way that an increase in temperature increases the speed of sound.