A Musical Sound Wave
Sound waves are longitudinal waves because these waves travels through the particles of the medium through which the sound is transported.
These waves vibrate parallel to the direction of motion of sound. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air. A sound wave is a phenomenon, which transports energy from one location to another without transporting matter.
Sound is produced by the vibration of objects. When objects vibrate, it collides with the molecules in the medium. This collision produces mechanical oscillations in the medium, due to which, the sound waves are known as mechanical waves. These sound waves cannot travel through vacuum, and they need material medium for propagation.
A sound wave traveling through air will cause a pressure variation in the air. The air motion which accompanies the passage of the sound wave will be back and forth in the direction of the propagation of the sound, which is the characteristic of longitudinal waves. The crests of the sine curve correspond to compressions; the troughs correspond to rarefactions; and the “zero point” corresponds to the pressure that the air would have if there were no disturbances moving through it. Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. The pressure of sound in air can be measured using a microphone.