How Sound Works –
Sound is a vibration that begins with some mechanical movement, like
slapping your hand down on a table. The atoms next to where your hand
hit the table vibrate, causing adjacent atoms to vibrate.
QUESTIONS: How Sound Works –
Have you ever heard of the sound barrier? Aircraft are said to be
breaking the sound barrier when they travel faster than the speed of
sound, a speed known as Mach 1.
Pitch and Frequency –
Two important words to know when talking about sound are pitch and
frequency. Frequency means how fast the sound wave is vibrating.
Frequency is not the same as the speed at which sound travels.
QUESTIONS: Pitch and Frequency –
When we talk, obviously, we are also creating sound. Producing
discernable speech is a complicated process involving many parts of the
Sound Waves –
A sound wave is a kind of wave that can be detected by the ears of
many creatures. A sound wave begins with some mechanical movement,
like plucking a guitar string.
QUESTIONS: Sound Waves –
Sounds waves are longitudinal waves. This means that as atoms vibrate
and pass energy from atom to atom, the wave that they cause moves in
the same direction as the vibration.
How We Hear Sound –
Hearing is the sense that we use to perceive sound. We hear something
when our ears translate sound waves into something that is
comprehensible to our brain.
QUESTIONS: How We Hear Sound –
In addition to fluid, the inner ear contains an
organ called the cochlea, which uses little
hairs that vibrate with sound waves in the fluid
to translate sound vibrations into electrical
signals that the nerves then send to the brain.
Breaking the Sound Barrier –
It took nine flights before Yeager broke the sound barrier. The first took
place on August 29th, 1947. Each subsequent flight was faster by .2 Mach.
Mach is the unit in which the speed of sound is measured.
QUESTIONS: Breaking the Sound Barrier –
When the Glamorous Glennis reached Mach 1.06, about 700 mph, on October 14th,
1947, the crew on the ground heard a loud boom, the first sonic boom.
The craft flew at supersonic (greater than sound) speed for 20 more
seconds before Yeager cut the engines and glided safely back down to
The Sound Barrier –
The term sound barrier was first used during World
War II when aircraft first began to try to travel faster
than the speed of sound. As they approached the
speed of sound, about 758 mph, they would begin to
encounter the aerodynamic effects of
QUESTIONS: The Sound Barrier –
Aircraft are said to be breaking the sound barrier when they travel faster
than the speed of sound, a speed known as Mach 1. The Mach unit of
measurement is named for Austrian physicist and philosopher Ernst Mach.
Sonic Boom –
A sonic boom is the sound you hear when an object
moves faster than the speed of sound. It is usually associated with military
aircraft flying at supersonic speeds.
QUESTIONS: Sonic Boom –
A sonic boom creates a very large amount of sound energy, as much as
a million watts per square meter. The volume sometimes exceeds 200
An ultrasound (also called sonography) is a
medical procedure that uses high-frequency
sound waves to make pictures of the inside of the
QUESTIONS: Ultrasound –
The most common use of ultrasound is on pregnant women. With an
ultrasound, a doctor can monitor fetal development. Ultrasounds can also
used to detect problems in certain fetal organs.
Sound Waves vs. Light Waves –
Two of the most basic things that physicists study are light and sound.
Many more advanced studies in physics have their basis in our
understanding of how light and sound work.
QUESTIONS: Sound Waves vs. Light Waves –
Besides being slower, sound waves are also able to travel through
substances (solids, liquids, and gases) that light waves are not. Light
moves best through empty space.
The study of how sound moves and behaves is called acoustics. Just as
ripples of water move away from a rock that is thrown into a pond, sound
waves travel away from the source of sound through both air and solids.
QUESTIONS: Acoustics –
The term acoustics also refers to the science of
controlling noise in buildings. Acoustics does more
than just minimize the extent to which sound travels.