Sound is a vibratory motion of the air or any other media, it does not travel
in a vacuum. The sound is determined by vibrating bodies and transmitted
to our ears without sensible motions of the air. At this point our ears start to
vibrate, and this vibration is interpreted by the brain as sound. Clearly vibratory phenomena have waveform. We may say that sound waves travel through
air almost in the same way as water waves travel through water. An acoustic
resonator is a device that exhibits resonance or resonant behavior, that is, it
naturally oscillates at some frequencies, called its resonant frequencies, with
greater amplitude than at others. It is used in order to enhance the eect of
the vibrations of the air and make the sound more clear. The oscillations in an
acoustic resonator are mechanical. Resonators are used to either generate waves
of specic frequencies or to select specic frequencies from a signal. Musical in-
struments use acoustic resonators that produce sound waves of specic tones. A
sound wave has the same characteristics as any other type of waveform: wave-
length, frequency, and amplitude. The wavelength is the distance from one crest
to another of a wave. The frequency of sound is the rate at which the waves pass
a given point, i.e. it is the number of oscillations (cycles) that occur each second
of time. The amplitude, is the peak deviation of the function from zero. The
simplest representation of a sound wave at a xed point of the space is given by
the sine wave, that is a sinusoid. Its most basic form as a function of time t is: