Sound, in its most fundamental form, is produced when something vibrates. The vibrating body causes the medium (water, air, etc.) around it to vibrate. Vibrations in air are called traveling longitudinal waves, which we can hear. Sound waves consist of areas of high and low pressure are called compression and rarefaction, respectively.
Throughout this site we will go over the details of sound waves and their connection to music theory, the different properties of sound, and how humans interpret sound.