Sound is a longitudinal wave. This means that the particles of the medium through which sound travels (such as air, water, or solids) vibrate back and forth in the same direction as the wave is moving. These vibrations create regions of compression (high pressure) and rarefaction (low pressure) that propagate the sound energy through the medium

. Additionally, sound waves are mechanical waves because they require a medium to travel through, relying on the mechanical vibrations of particles to transmit energy. They are also pressure waves due to the alternating compressions and rarefactions in the medium

. In summary, sound waves are longitudinal mechanical pressure waves that propagate through a medium by particle vibrations parallel to the direction of wave travel.