Transcript The Physics of Sound Wave a disturbance that transfers energy from

The Physics of Sound
Wave
a disturbance that transfers
energy from place to place.
The material through which a wave
travels is called a medium.
Ex. Gases (air), liquids (water) and
solids (rope)
Waves that require a medium
through which to travel are called
mechanical waves.
TRANSVERSE
A wave that moves the medium
in a direction perpendicular to the
direction in which the wave travels.
LONGITUDINAL
A wave that moves a medium
in a direction parallel to the
direction in which the wave travels.
Define Sound
A disturbance that travels
through a medium as a
longitudinal wave.
The Physics of Sound
Longitudinal Wave
The Physics of Sound
How does sound travel?
1. Sound waves carry energy through a
medium.
2. Each particle of the medium vibrates as
the disturbance passes.
3. When the disturbance reaches your ears,
you hear the sound.
What is an echo?
• A reflected sound wave is called an
ECHO.
• Reflection – when an object or a wave
hits a surface through which it cannot
pass, it bounces back.
Explain why you don’t always
here an echo?
• There are often soft materials that absorb
the sound waves in a room
What are two ways sound
diffracts?
1. Through an opening in a barrier such as a
doorway or
2. Bend around corners
Diffraction - the spreading or bending of a
wave around a corner.
What is the Speed of Sound
• 343 m/s in air at 20°C
Three factors that affect speed
1. Elasticity
2. Density
3. Temperature
How does elasticity affect speed
of sound?
• The more elastic the faster sound will travel
in the medium
– Travels fastest in solids
– Travels slower in liquids and gases because
they are usually not as elastic
How does density affect speed of
sound?
• Sound travels slower the denser the medium
How does temperature affect
speed of sound?
• Sound travels more slowly at lower
temperatures than at higher temperatures
Properties of Sound
Define loudness
Loudness – describes what you hear and is
measured in decibels (dB)
Sound depends on 2 factors
1.
2.
The amount of energy it takes to make the sound
The distance from the source of the sound
Explain how energy and distance
affect loudness
Energy
– the greater the energy the louder the sound
– larger amplitude = larger sound
Distance
– loudness increases the closer you are to the
source
– a sound wave of greater intensity sounds
louder
How is Sound Measured?
DECIBEL SCALE
100
70
40
0
10
18
80
110
120
What is Pitch?
•
Pitch – a description of how high or how low
the sound seems to a person
How does Frequency affect pitch?
–
Depends on the frequency of the sound wave
•
•
high frequency = high pitch
low frequency = low pitch
How do we change the pitch of our voice?
•
•
•
use vocal cords located in larynx to change sounds
stretched vocal cords = higher frequency sound with high
pitch
relaxed vocal cords = lower frequency sound with low
pitch
What is the Doppler Effect
the change in frequency due to the relative
motion of the wave source and the observer
The observed frequency is higher when the
source and observer are getting closer.
The observed frequency is lower when the
source and observer are getting farther away.
What causes the Doppler Effect?
1. when a sound source moves, the
frequency of the waves changes
because the motion of the source adds
to the motion of the waves.
2. as source moves toward listener the
frequency of the waves is higher (ex.
Ball)
Click here and here
to run simulations of the Doppler Effect.
The Doppler Effect
can be evident for
all types of waves –
including light,
sound, water, etc…
Anatomy of the Human Ear
Anatomy of the Human Ear
anvil
- (also called the incus) a tiny bone that passes vibrations from the hammer
to the stirrup.
cochlea - a spiral-shaped, fluid-filled inner ear structure; it is lined with cilia
(tiny hairs) that move when vibrated and cause a nerve impulse to form.
eardrum - (also called the tympanic membrane) a thin membrane that vibrates
when sound waves reach it.
Eustachian tube - a tube that connects the middle ear to the back of the
nose; it equalizes the pressure between the middle ear and the air outside. When
you "pop" your ears as you change altitude (going up a mountain or in an airplane),
you are equalizing the air pressure in your middle ear.
hammer - (also called the malleus) a tiny bone that passes vibrations from the
eardrum to the anvil.
nerves - these carry electro-chemical signals from the inner ear (the cochlea) to
the brain.
outer ear canal - the tube through which sound travels to the eardrum.
pinna - (also called the auricle) the visible part of the outer ear. It collects sound
and directs it into the outer ear canal
semicircular canals - three loops of fluid-filled tubes that are attached to
the cochlea in the inner ear. They help us maintain our sense of balance.
stirrup - (also called the stapes) a tiny, U-shaped bone that passes vibrations
from the stirrup to the cochlea. This is the smallest bone in the human body (it is
0.25 to 0.33 cm long).
How does Human Hearing
Work?
sound wave
vibrates ear drum
amplified by bones
(Hammer, Anvil , Stirrup)
converted to nerve
impulses in cochlea
by cillia
Healthy Cochlea
The cilia ( sensory
hairs) appear normal
Damaged Cochlea
Loss of cilia as a
result of Noise
Why does hearing loss occur?
• Damaged ear drum, infections, extended
exposure to loud noise and age
• Most common form is gradual due aging.
Cillia in ears die and no longer send signals
to brain.
Name and describe 3 ways
sound is used?
• Echolocation – the use
of reflected sound
waves to determine
distances or locate
objects.
• Some animals,
including bats and
dolphins, use
echolocation to
navigate and to find
food.
Using Sound
• Ultrasound technologies such as sonar and
ultrasound imaging are used to observe
things that cannot be seen directly.
Using Sound
Ultrasound imaging – devices send ultrasound waves into
the body and detect the reflected sound waves. The
device uses the reflected ultrasound waves to create a
picture called a sonogram.
Sonar – a system that uses reflected sound waves to detect
and locate objects underwater.
• Sonar is used to determine the depth of water, to map the ocean
floor, and to locate sunken ships, schools of fish, and other
objects in the ocean.
“Seeing” with Sound
Medical
Imaging
SONAR
“Sound Navigation
Ranging”
• 1. Draw and Label the parts of the human
ear
• 2. Explain how human hearing works
• 3 What are some causes of hearing loss?
• 4. What is the most common cause of
hearing loss? Explain what happens to the
ears as we age.
• 5. Name and describe 3 uses of sound.