Download Sound Waves PowerPoint

WHAT IS SOUND?
• All sounds are created by vibrations
A vibration is the
complete backand-forth motion of
an object.
• A sound wave is a longitudinal wave
caused by vibrations and carried through a
substance
• Sound waves travel in all directions away
from their source.
• Air or other matter does not travel with the
sound waves.
Why not…?
MEDIUM
• All sound waves
require a medium.
•A medium is a
substance through
which a wave can
travel.
Sound waves
vibrate the eardrum
The eardrum
vibrates the
hammer, anvil
and stirrup
The stirrup
vibrates the
oval window.
The liquid
makes
hairs inside
bend.
The oval
window makes
waves in the
cochlear liquid.
Hair
stimulates
nerves
which
send
messages
to the
brain.
Jay-Z,
Don’t these
earrings make my
outer ear look so
fly?
Check for Understanding…
• What is the job of the outer ear?
• What is the job of the bones in the middle
ear?
• What is the job of the inner ear?
OUTER EAR…
• COLLECT & DIRECT!
I collect da
ladies and
direct da
videos!
MIDDLE EAR…
• INCREASE THE SIZE OF VIBRATIONS.
How…? (Hint: they are a type of simple
machine!)
INNER EAR…
• Convert vibrations into electric signals.
Hearing Loss & Deafness
• Exposure to loud sounds
can cause Tinnitus.
• The hair cells in the
cochlea are permanently
damaged.
PROTECT YOUR HEARING!
PROPERTIES OF SOUND
• SPEED
• PITCH & FREQUENCY
• LOUDNESS & AMPLITUDE
SPEED
Look at the chart…In what state of
matter does sound travel fastest?
What is the relationship between
temperature and speed of sound?
- The Nature of Sound
Temperature and the Speed
of Sound
•The speed of sound in
dry air changes as the
temperature changes.
The graph shows data
for the speed of sound
in air at temperatures
from –10ºC to 20ºC.
FREQUENCY & PITCH
Remember –frequency is the number of waves in a given
time.
Frequency is measured in Hertz. 1 Hz = 1 wave/ second.
Low note on a
piano 40 Hz
Screech of a
bat 10,000 Hz
Frequency & Hearing
• Sounds too high to hear are called
ultrasonic
The Doppler Effect
The APPARENT change in the frequency of a
sound caused by the motion of either the
listener or the source.
What is sound?
1
The Doppler Effect
• The change in frequency that occurs when a
source of sound is moving relative to a listener
is called the Doppler effect.
• The Doppler effect occurs whether the sound
source or the listener is moving.
What is sound?
1
The Doppler Effect
• As you move closer you encounter each
sound wave a little earlier than you would if
you were sitting still, so the sound has a
higher pitch.
• When you move away from the sound, each
sound wave takes a little longer to reach you.
• You hear fewer wavelengths per second,
which makes the sound lower in pitch.
What is sound?
1
The Doppler Effect
• Radar guns that are used to measure the
speed of cars and baseball pitches also use
the Doppler effect.
• When the radio wave is reflected, its
frequency changes depending on the speed
of the object and whether it is moving
toward the gun or away from it.
• The radar gun uses the change in frequency
of the reflected wave to determine the
object’s speed.
LOUDNESS & AMPLITUDE
• Loudness is a measure of how well a
sound can be heard.
• Loudness is measure in decibels
• The larger the amplitude of a sound wave
the louder the sound.
• An increase in the loudness
of a sound of 10 dB means
that the energy carried by
the sound has increased ten
times, but an increase of 20
dB means that the sound
carries 100 times more
energy.
• Hearing damage begins to
occur at sound levels of
about 85 dB.
• The amount of damage
depends on the frequencies
of the sound and the length
of time a person is
exposed to the sound.
“Seeing” Amplitude & Frequency
INTERACTIONS OF
SOUND WAVES
- The Nature of Sound
Interactions of Sound Waves
• Sound waves reflect off objects, diffract
through narrow openings and around
barriers, and interfere with each other.
What is sound?
1
Echoes
• A reflected sound wave is called an echo.
• If the distance between you and a reflecting
surface is great enough, you might hear the
echo of your voice.
• This is because it might take a few seconds
for the sound to travel to the reflecting
surface and back to your ears.
What is sound?
1
Echoes
• Sonar systems
used sound
waves to map
objects
underwater.
What is sound?
1
Echoes
• By measuring
the length of
time between
emitting a pulse
of sound and
hearing its echo
off the ocean
floor, the distance to the
ocean floor can be measured.
1
Echolocation
Some animals use a method called
echolocation to navigate and hunt.
Bats, for example, emit high-pitched
squeaks and listen for the echoes.
The type of echo it hears helps the bat
determine exactly where an insect is.
What is sound?
1
Echolocation
• People with visual impairments also use
echolocation.
• Using their ears, they can interpret echoes
to estimate the size and shape of a room,
for example.
• Some animals, including bats and
dolphins, use echolocation to
navigate and to find food.
1
Using Sound Waves
• Sound waves can be used to treat certain
medical problems.
• A process called ultrasound uses highfrequency sound waves as an alternative
to some surgeries.
What is sound?
1
Using Sound Waves
• For example, some people develop small,
hard deposits in their kidneys or gallbladders.
• A doctor can focus ultrasound waves at the
kidney or gallbladder.
• The ultrasound waves cause the deposits to
vibrate rapidly until they break apart into
small pieces.
What is sound?
1
Using Sound Waves
• Ultrasound can be
used to make images
of the inside of the
body.
• One common use of
ultrasound is to
examine a developing fetus.
• Also, ultrasound along with the Doppler effect
can be used to examine the functioning of the
heart.
2
Resonance
• Sometimes sound
waves cause an
object to vibrate.
• When a tuning fork is
struck, it vibrates at
its natural frequency
and produces a sound
wave with the same
frequency.
2
Resonance
• Suppose you have two tuning forks with the
same natural frequency.
• You strike one tuning fork, and the sound
waves it produces strike the other tuning fork.
• These sound waves would cause the tuning
fork that wasn’t struck to absorb energy and
vibrate.
• This is an example of resonance.
Resonance
• Resonance occurs when an object is made to
vibrate at its natural frequencies by absorbing
energy from a sound wave or another object
vibrating at these frequencies.
• Musical instruments use resonance to amplify
their sounds.
2
Overtones
• A tuning fork produces a single frequency,
called a pure tone.
• The notes produced by musical instruments
are not pure tones.
• Most objects have more than one natural
frequency at which they can vibrate.
• As a result, they produce sound waves of
more than one frequency.
2
Overtones
• If you play a single note on a guitar, the pitch
that you hear is the lowest frequency produced
by the vibrating string.
• The lowest frequency produced by a vibrating
object is the fundamental frequency.
• The vibrating string also produces higher
frequencies.
Overtones
• These higher frequencies
are called overtones.
• Overtones have
frequencies that are
multiples of the
fundamental frequency.
Overtones
• The number and
intensity of the overtones
produced by each
instrument are different
and give instruments
their distinctive sound
quality.
A sonic boom is the name for the explosive sound
you hear when a shock wave reaches your ear.
SOUND QUALITY
• The result of several pitches mixing
together is called sound quality.
Sound quality differs when two
instruments play the same note.
MUSIC OR NOISE?
Noise can be described as any sound,
especially a nonmusical sound, that is a random
mix of frequencies (or pitches).
- How You Hear Sound
The Human Ear
• The outer ear funnels
sound waves, the
middle ear transmits
the waves inward, and
the inner ear
transforms sound
waves into a form that
travels to your brain.
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