Sound is Vibration
Vibrations produce sound, and sound produces vibrations. These vibrations are also known as sound waves. When an object begins to vibrate, it moves forward and pushes the air molecules that are in front of it closer together causing an area of compression. Then the object moves back and leaves the area with fewer air molecules which spread farther apart: this is called rarefaction.
One vibration consists of one forward motion and backward motion. A series of these vibrations, also called sound waves, transfer sound energy from the sound source to another location, such as a person’s ear. Sound waves travel in all directions away from their sources. If the distance is too great, sound waves eventually vibrate so weakly they are inaudible.
**Sound waves are the result of vibrations. The sound wave is a series of compression and rarefaction areas traveling through a substance.
Compression: air molecules close together
Rarefaction: air molecules far apart
Inaudible: cannot be heard
Vibration: one forward and backward motion
The diagram below shows a sound wave with areas of compression and rarefaction.
Below a tuning fork is vibrating and sending out sound waves.
How do we hear?
An object, such as a tuning fork, causes air molecules to vibrate, which causes eardrum to vibrate.