Sound
Chapter 24
24-1 What is Sound?
 I can explain how sound waves are produced.
 I can describe how sound waves are
transmitted.
 I can compare the phases of matter as to
their ability to transmit sound
 I can describe how the speed of sound is
affected by the density of the medium through
which it travels.
How sounds are made…
 Sound is produced when matter vibrates.
 As an object vibrates, it gives energy to the
particles of matter around it.
 Sound is a longitudinal wave.
 It moves with a series of compression and
rarefactions.
Sound Waves
Molecules in the air vibrate about some average
position creating the compressions and rarefactions.
We call the frequency of sound the pitch.
 Anything that vibrates produces sound.
 When you speak, your vocal cords vibrate.

Particles of air simply move back and forth.
 A radio would NOT work in outer space
because there is not any medium for sound to
travel through.
 “If a tree falls in the forest and no one is
present to hear it, is there a sound?”
Speed of Sound
 Determined by the temperature, elasticity,
and density of the medium.
 Temperature


Sound travels slower in lower temperature
Sound travels faster in higher temperature
 Average speed of sound in air = 340 m/s
Medium
Speed (m/s)
Air
343
Helium
972
Water
1500
Steel
5600
Elasticity & Density
 Sound can travel through any medium.
 Greatest speed in solids, slowest speed in
gases.
 Fastest in more elastic mediums, solids are
more elastic.
 In materials of the same phase, the more
dense the slower the waves travel.
24-1 What is Sound?
 I can explain how sound waves are produced.
 I can describe how sound waves are
transmitted.
 I can compare the phases of matter as to
their ability to transmit sound
 I can describe how the speed of sound is
affected by the density of the medium through
which it travels.
Book Work
 24-1 Section Review

Page 618
#1-4

Section 24-1 Worksheet

24-2 Properties of Sound
 I can describe the properties of sound waves.
 I can explain how frequency and pitch are
related.
 I can describe the Doppler effect.
Frequency & Pitch
 Sounds can be described by high or low
pitches.
 Pitch depends on how fast the particles of
the medium vibrate.
 Pitch is the number of waves in a given
amount of time, also known frequency.
 Meaning the pitch depends on the frequency.
Pitch
 A measure of how high or low a sound is
 Pitch depends on the frequency of a sound wave
 For example,
- Low pitch
- High pitch
- Low frequency
- High frequency
- Longer wavelength
- Shorter wavelength
Doppler Effect
 Police car speeding by:

Higher pitch as approached, lower pitch as
moving away.
 Change in pitch is referred to as the Doppler
effect.


Occurs whenever there is motion between the
source of a sound and its receiver.
Source or receiver must be in motion.
Doppler Effect
 Police car moving towards you, pushing waves
together causing:

Shorter wavelengths, higher freq., higher pitch.
 Police car moving away from you, spreading
waves out:

Longer wavelengths, lower freq., lower pitch
Loudness
Chart
Loudness is
related to the
amount of
energy
carried by a
wave.
24-2 Properties of Sound
 I can describe the properties of sound waves.
 I can explain how frequency and pitch are
related.
 I can describe the Doppler effect.
Terms to Know
Pitch
Doppler Effect
Book Work
24-2 Section Review
•Page 623
• #1-4
• Name that Sound
Worksheet
24-6 How You Hear
 I can identify the parts that make up the ear.
 I can explain how vibrations are converted
into electrical signals.
For Sound to be heard…
 You need 3 things:



1. a source that produces the sound
2. a medium to transmit the sound
3. an organ of the body that detects the sound
 Sound enters the outer ear, vibrates
eardrum, enters middle ear and vibrates
liquid-filled inner ear.
Human Ear
Outer Ear
 The outer ear acts as funnel for the waves.
 The waves travel through the ear canal and hit
the lightly stretched membrane called the
eardrum causing it to vibrate.
 The vibrations then
enter the middle ear.
Middle Ear
 The middle ear contains the 3 smallest
bones in the body.

hammer, anvil, stirrup
 The vibrations travel
through the 3 bones
and are transmitted to
a liquid-filled inner ear.
Inner Ear
 The inner ear contains
the cochlea.
 Cochlea is snail shaped
 Contains liquid and
hundreds of cell
attached to nerve fibers
 The nerve fibers form
one larger nerve that
travels to the brain
where they are
interpreted as sound
Human Ear
24-6 How You Hear
 I can identify the parts that make up the ear.
 I can explain how vibrations are converted
into electrical signals.
Chapter Review Pg 638
 Multiple Choice

#2-5, 9-10
 True or False

#1-4, 6
After Chapter Review is
turned in…
- Study vocabulary words
 Concept Mastery

#1-4