B _ _ _ _ hears sound.

Describes how high or low a sound is. ( loud , pitch)

as the bell rings, its vibrations result in spaces where air particles are squeezed together and spaces where air particles are spread apart. This movement of particles makes a kind of wave called a c _ _ _ _ _ _ _ _ _ _ w _ _ _

M_ _ _ _ _ vibrates.

S _ _ _ _ waves travel.

A movement back and forth. (vibration, wave)