The document discusses sound and how it is produced, transmitted, and heard. It describes how sound is a longitudinal wave that travels through matter by causing compressions and rarefactions in molecules. The speed of sound depends on the temperature, density, and elasticity of the medium, being fastest in solids and slowest in gases. It also discusses how the human ear detects sound waves, with the outer ear funneling sound to the eardrum, middle ear bones vibrating the fluid-filled inner ear, and inner ear hair cells converting this into electrical signals sent to the brain.

1. Sound
Chapter 24

2. 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.

3. 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.

4. Sound Waves
Molecules in the air vibrate about some average
position creating the compressions and rarefactions.
We call the frequency of sound the pitch.

5.  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?”

6. 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

7. Medium Speed (m/s)
Air 343
Helium 972
Water 1500
Steel 5600

8. 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.

9. 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.

10. 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.

11. 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.

12. Pitch
 A measure of how high or low a sound is
 Pitch depends on the frequency of a sound wave
 For example,
- Low pitch
- Low frequency
- Longer wavelength
- High pitch
- High frequency
- Shorter wavelength

13. 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.

14. 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

15. Loudness
Chart
Loudness is
related to the
amount of
energy
carried by a
wave.

16. 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.

17. 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.

18. 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.

19. Human Ear

20. 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.

21. 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.

22. 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

23. Human Ear

24. 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.