We have all heard that refreshing crackling sound when we throw ice cubes in our drink.  But what causes this sound?

The outer edges and surface of the ice cube will be the first areas to experience the drastic temperature shift between the room-temperature drink and the ice.  These will begin to engage in heat exchange. The ‘cracking’ sound you hear when you pour that liquid over the ice is caused by a phenomenon called ‘differential expansion’. More specifically, the outer edges of the ice will begin to contract as the temperature rises, essentially melting and breaking the firm bonds that are maintaining it in a solid state.  On the inside of the ice cube, however, the temperature remains below zero degrees Celsius, and there is no immediate change to the structure or integrity of those bonds.

The warming of the outside of the solid ice cube happens faster than the warming of the inside of the ice cube. The solid ice cube cannot handle the differences in the density caused by the varying temperatures. The pressure of this causes the solid ice to crack making that satifying sound which is used in many drinks commercials.