Galileo, an Italian astronomer and physicist, was the greatest contributor
to our understanding of sound. He demonstrated that the frequency of sound
waves determined the pitch. This was done by scraping a chisel across a brass
plate producing a screech. Galileo then related the spacing of the grooves
induced by the chisel to the pitch of the screech.
DaVinci - (1500) discovered that sound travels in waves
Marin Mersenne - (1640) first measured the speed of
sound in air.
Boyle - (1660) discovered that sound waves must travel in a medium
Newton - (late 1660's) formulated a relationship between the speed of sound in
a medium and the density and compressibility in a medium.
Bernoulli - (mid 1700's) explained that a string could vibrate at more than one
Making sound waves:
The man-made processes in which sound can be made are ultrasound and simple
noises. Many transducers can convert ultrasonic waves into electric waves. They
give off strong echoes that create stronger electric pulses than weak ones do.
A special computer registers the data that the pulses and echoes give off. Then
the computer can give information on the substances that reflected the
ultrasonic waves. Air that is passed through the vocal cords causes them to
vibrate. Longitudinal vibration of the vocal chords makes surrounding air
Sound is used in:
Sound waves are used when performing ultrasound tests. Ultrasound tests are
used on pregnant women to detect many structural and functional abnormalities
in a fetus. Ultrasound may also aid in the detection of heart disease, tumors,
gall stones, and other disorders.
Ultrasound is used by manufacturers to measure
the wall thickness of metal or plastic pipes and to test the concentration of
particles in inks and paints. Sonar devices locate schools of fish, enemy
ships, and underwater obstacles through the use of ultrasound. Geophysicists
can use sound in exploring for minerals and petroleum and also locate possible
mineral or oil bearing rock formations. One way to use sound in industry is
through music. Music is based on sound waves which are used in instruments and
Scientists have invented whistles and other
devices that produce ultrasound. An ultrasonic transducer converts electric
energy into ultrasonic waves. These waves can also be converted into electric
energy by transducers. One way to use the sound wave in science is a sonar
wave. A sonar wave uses a sound wave to see how far or deep something is. This
is mainly used for underwater research.
Today's Use of Sound Technology
Telephone, Motion Picture, Telephone, C.D.'s
Televisions, Phonographs, Electronics, Hearing Aids,
Video Tape Recorders, Video Cameras, Speakers, Stethoscopes
Recording and Reproducing Sound
The essential components of sound recording
and reproduction are the microphone, speaker and amplifier. A microphone
changes sound waves into electric signals that correspond to a patterns of the
waves. The speaker changes those electric signals produced by a microphone back
into sound. An amplifier strengthens the electric signals to increase the
volume. Every phonograph, public address system, radio, tape recorders,
television, and sound system must have an amplifier and speaker.
The Acoustic Thermometry of Ocean Climate project was designed to map out
global ocean temperatures using sound waves, but concerns were brought up that
it may harm various marine mammals. Excessively loud sound can cause ear
damage, which may sometime lead to brain damage. Constant noise, even if it is
not extremely loud, can cause fatigue, hearing loss, irritability, nausea, and
tension. People exposed to loud noise for a long period of time may suffer from
temporary or permanent loss of hearing.
One should protect ears from the dangers associated to sound by not
listening to overly loud music. . Thick, heavy walls block noise. A precaution
that we take to protect ourselves and the environment from the dangers of sound
waves is using a muffler on a car, to help quiet car engines, wearing ear plugs
when a loud noise is constantly around us.
A Sonic Boom:
A sonic boom is the thunder-like noise that a person
may hear when an airplane flies over the individual at a supersonic rate. (
faster then the speed of sound.) A sonic boom is caused when a shock wave forms
a cone of pressurized air molecules which move in all directions. When the cone
spreads across the landscape, it creates a continuous sonic boom around the
full width of the cone's base. The sharp release of pressure after the buildup
by the shock wave is known as a sonic boom.
Acoustic research of the 1970's included the study of new uses of
ultrasound, and the development of better ultrasonic equipment. In the 1980's,
research included the design of better sound reproducing equipment and the
development of computers that can understand and reproduce speech.
Science News ( Nov 19, 1994)
Scientists are trying to develop a way to get more informative images from
ultrasound by deriving 3 dimensional images from sequences of ultrasound scans.
Researchers from all over the world are working on this concept. Right now, a
number of technological obstacles stand in the way of developing such a
process. Tracking equipment is still too imprecise and computers can't generate
the 3 dimensional images fast enough.