The energy or push from the sound of the word keeps going down a whole row of molecules, pushing them further and further down the row. Meanwhile, the first molecules go back to their original positions. Sound waves travel through the air by vibrating or moving the particles of matter in the air. If there were no particles in the air, there would be no sound made. We are able to hear sound waves between 20 and 20,000 waves per second.
Frequency is a term for the number of vibrations per second.
If it is more than 20,000 waves per second, it is ultrasonic. The sound of music differs from noise in that the sound waves are regular and ordered. This makes songs recognizable and pleasing to the ear.