In Acoustics and Vibration, most periodic waves, regardless of the form
, can be represented by two or more sine waves. Most
waves can be reduced to simple harmonic or sine wave
components which generally form harmonic series. They have
frequencies which are integral multiples of the lowest
frequency. The lowest frequency is called the fundamental
and the higher ones are called harmonic.

The Frequencyof a vibrating
body is the number of cycles of motion in a unit time.

The Period of a wave is the
time elapsed while the motion repeats itself. It is the
reciprocal of the frequency

The Amplitude of a wave is the
shortest distance between twp particles along the wave which
differ in phase by one cycle.

The number of independent coordinates
necessary to describe the motion of a system is called the
degrees of freedom. Examples of systems with various degrees
of freedom with a mass "M" are shown below.

Example (D) is a single degree of freedom
with a mass "m" supported on frictionless and
mass-less rollers attached to a spring and a dashpot.