Sound is produced by the vibration of objects and travels as longitudinal waves through a medium. As the particles of the medium vibrate, they alternately come closer together (compression) and move farther apart (rarefaction), transmitting the sound wave. The key characteristics of sound waves include amplitude, frequency, wavelength and velocity.

2. How is Sound produced?
Sound is produced due to the vibration of objects.
Example: the sound of human voice is produced due to the vibration of the vocal
cords.
Propagation of Sound
-The sound produced by a vibrating object travels through a medium
to a listener.
-When an object vibrates, the particles around the medium vibrates. The
particle in contact with the vibrating object is first displaced from its
equilibrium position.
-A wave is a disturbance which moves through a medium by the vibration of
the particles of the medium.

3. Sound waves are composed of compression and rarefaction patterns.
Compression happens when molecules are densely packed together.
Alternatively, rarefaction happens when molecules are distanced from one
another.
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Compression & Rarefaction
Sound Waves
The sound produced by a vibrating object travels through a medium to a listener.
-When an object vibrates, the particles around the medium vibrates. The particle in
contact with the vibrating object is first displaced from its equilibrium position.
-A wave is a disturbance which moves through a medium by the vibration of the particles
of the medium.

4. A longitudinal wave is one where all the particles of the medium (such as gas, liquid
or solid) vibrate in the same direction as the wave. Sound waves are longitudinal
waves. When longitudinal waves travel through any given medium, they also include
compressions and rarefactions.
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Longitudinal Waves
Transverse Waves
Transverse waves A mechanical wave is transverse when all the
particles of the medium, which are solid or liquid (and never gas),
vibrate perpendicularly at right angles, up and down, and
continue to move in the direction of the wave.

6. Sound waves have several characteristics. These include amplitude, frequency, time, velocity
and wavelength. The most important characteristic of a sound wave is wavelength. How we
hear sound
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What are the characteristics of sound waves?

7. Also known as acoustic intensity, it is the power carried by sound waves per unit in a direction
perpendicular to that area, the SI unit of intensity which includes sound intensity is the watt per
square meter.
S o u n d I n t e n s i t y
1.What is the intensity of Sound 4m away from a 500W speaker?
How much energy is absorbed by the eardrum per minute if the surface of the ear is 60mm^2?

8. 2. The sound intensity is 3x 10^ -6 W/m^2 at a distance of 10m away from the source. How
much power is emitted by the source?
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9. 3.The intensity of a sound wave is 100W/m^2 at a distance of 3m.
A.What is the intensity of the sound wave at a distance of 6m?
B.What is the intensity at 9m?
A d d i t i o n a l A c t i v i t y

10. R e f e r e n c e s
Physics for Scientists and Engineers with Modern Physics (9th Ed.)
by Reymond A. Serway & John W. Jewett, Jr.
Brooks/Cole
20 Channel Center Street
Boston, MA 02210
USA
Sound Intensity Physics Problem