Sound is a wave of vibrations that spreads from its source. The vibration is a back-and-forth motion, and sound waves have areas where particles are close together called crests. The number of crests that pass per second is the frequency, with a higher frequency creating a higher pitch. Louder sounds come from sources that vibrate more and have more energy, while loudness can be measured in decibels. Your vocal cords vibrate when talking, caused by air rushing past them, making air particles around them vibrate and travel as sound waves. Sound can travel through solids, liquids and gases but not vacuums, and its speed depends on the material. For sound to be heard, an object

1. CHAPTER 14 SECTION 2

2. SOUND
–a wave of vibrations that spreads from
its source.
• Vibration is the back-and-forth motion of
an object.

3. Crest - areas where particles are very
close together
Frequency - The number of crests that
pass by a point each second
The greater the frequency is, the higher
the pitch of the sound

4. Why Are Some Sounds Louder
Than Others?
• The source of the louder sounds
is vibrating more.
• These sound waves have more
energy.
• A sound’s loudness can be
measured in units called
decibels.

5. YOUR VOICE
• Your vocal cords vibrate when you talk.
• The vibrations are caused by air rushing past
them.
• Your vocal cords make the particles in the air
around them vibrate.
• These vibrations travel outward through the
air as sound waves.

7. How Does Sound Behave?
• Sound can travel through solids,
liquids, and gases
• It cannot travel through a vacuum,
which is empty space that contains no
particles
• The speed at which sound waves
travel is different in different
materials.

8. Sound Transfers Energy
• For a sound to be heard, energy must first cause
an
object to vibrate.
• Vibrating objects give off energy in sound waves in
air.
• Some of the energy reaches your ear, and your
eardrum absorbs some of the energy.
• In this way, the energy
of the original material’s
vibrations passes to you.

10. SOUND
–a wave of vibrations that spreads from
its source.
• Vibration is the back-and-forth motion of
an object.

11. Crest - areas where particles are very
close together
Frequency - The number of crests that
pass by a point each second
The greater the frequency is, the higher
the pitch of the sound

12. Why Are Some Sounds Louder
Than Others?
• The source of the louder sounds
is vibrating more.
• These sound waves have more
energy.
• A sound’s loudness can be
measured in units called
decibels.

13. YOUR VOICE
• Your vocal cords vibrate when you talk.
• The vibrations are caused by air rushing past
them.
• Your vocal cords make the particles in the air
around them vibrate.
• These vibrations travel outward through the
air as sound waves.

14. How Does Sound Behave?
• Sound can travel through solids,
liquids, and gases
• It cannot travel through a vacuum,
which is empty space that contains no
particles
• The speed at which sound waves
travel is different in different
materials.

15. Sound Transfers Energy
• For a sound to be heard, energy must first cause
an
object to vibrate.
• Vibrating objects give off energy in sound waves in
air.
• Some of the energy reaches your ear, and your
eardrum absorbs some of the energy.
• In this way, the energy
of the original material’s
vibrations passes to you.