The pressure fluctuations in the air
are due to molecules of air vibrating back and forth about their original position but
passing on some of their energy of movement. From Eqns. (1) and (2), a particular molecule
has a displacement at time t of :
(5)
Then it is moving at a velocity of
vibration given by :
(6)
and is being accelerated at a rate :
(7)
Simple harmonic motion
is defined as a periodic motion in which :
(i) the acceleration is always
directed towards a fixed point in its path, and
(ii) the acceleration is proportional
to its distance from the fixed point.
