Sound is a pressure wave that is
created by a vibrating object.
These vibrations set particles in the surrounding medium (typical air) in
vibrational motion, thus transporting
energy through the medium.
Since the particles are moving in
parallel direction to the wave movement,
the sound wave is referred to as a
The result of longitudinal waves is the
creation of compressions and
rarefactions within the air.
The alternating configuration of C and
R of particles is described by the graph
of a sine wave (C~crests, R~troughs)
The speed of a sound pressure wave in the air is
331.5+0.6Tc m/s, Tc temperature in Celsius
The particles do not move down the way
with the wave but oscillate back and forth
about their individual equilibrium position.