Basic concept of sound

The transmission of sound can be explain using a toy reproduction consisting of an array of balls organized by springs. For a real material the balls stand for molecules and the springs stand for the bonds between them. Sound passes through the representation by compressing and increasing the springs, transmitting energy to neighboring balls, which transmit energy to their springs, and so on. The speed of sound through the model depends on the inflexibility of the springs (stiffer springs transmit energy more quickly). Effects like spreading and reflection can also be understood using this model.

In a real material, the inflexibility of the springs is known as the elastic modulus, and the mass corresponds to the density. All extra things being equal, sound will travel more slowly in denser materials, and faster in stiffer ones.