SOUND WAVES
Sound waves are produced by the vibration of an object, such as your vocal cords,
a plucked string, or a jackhammer. The vibrations cause pressure variations in the
conducting medium (which can be gas, liquid, or solid), and if the frequency is
between 20 Hz and 20,000 Hz, the vibrations may be detected by human ears. The
variations in the conducting medium can be positions at which the molecules of the
medium are bunched together (where the pressure is above normal), which are
called compressions, and positions where the pressure is below normal, called
rarefactions. In the figure below, a vibrating diaphragm sets up a sound wave in an
air-filled tube. Each dot represents a great number of air molecules.
That Sounds Fast
At sea level, the speed of
sound is 340 m/s.A pipe organ exploits the very phenomenon pictured and described above, to
generate different notes.
Longitudinal Waves
Unlike transverse waves, a
longitudinal wave travels
and oscillates in the