Transcript Sound - TeacherWeb

Sound
4th Grade Science
Sound
• Sound is produced when
energy causes particles to
vibrate.
• Sound carries energy.
• Sound travels in waves.
• These waves are different
than light waves.
• These waves travel
longitudinally.
Sound waves
• Sound waves move out in all directions from a
vibrating object.
• You hear something when the vibrations strike
your ear.
Longitudinal Waves
• Rarefaction
• Section of a longitudinal wave where the particles are less crowded
than normal
• Compression
• Section of a longitudinal wave where the particles are crowded
together
How does sound travel?
• Sound must have a
medium to travel.
• Sound cannot travel in
a vacuum.
• Sound travels at
different speeds.
• Sound travels in solids
fastest and gases the
slowest.
All sounds are not alike
• Wavelength dependent
• Frequency - Pitch
• Amplitude - Loudness
Frequency = Pitch
• Number of times a sound
source vibrates in one
second.
• Frequency determines
pitch.
• Pitch is the highness or the
lowness of a sound.
• A frog’s croak vs. a
kitten's meow
Amplitude = Loudness = Volume
• The amount of energy
in the sound wave
• Amplitude is related to
loudness of a sound.
• Loudness is measured
in decibels.
• Loud sounds can
damage your hearing.
How do we hear sound?
(Use worksheet)
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1. Outer Ear The outer ear
collects sound waves. It acts like a
funnel to direct sound waves into
the ear.
2. Eardrum Sound waves make
the eardrum vibrate like the head of
a drum.
3. Middle Ear The vibrating
eardrum makes three tiny bones in
the middle ear vibrate. They are the
hammer, anvil, and stirrup.
4. Inner Ear The little vibrating
bones pass sound vibrations along
to a tube that is filled with fluid in
the inner ear. The fluid then
vibrates. The vibrating fluid makes
tiny hair cells vibrate, too.
5. Nerve to Brain The vibrations
of the hair cells are passed along to
a nerve that carries sound messages
to the brain. The brain processes
the messages, and you hear sound.
Echoes, sonar and echolocation
• Echoes occur when
sound waves bounce
off of a surface and
they are heard again.
• Sonar is used with
bouncing sound waves
• Bats use echolocation
to find insects.
Tools and sound
• Stethoscopes
• Hearing aids
• Ultrasound
Sound quality - noise
• A pleasant sound has
a regular wave
pattern. The pattern
is repeated over and
over. But the waves
of noise are
irregular. They do
not have a repeated
pattern.
Sound
•Must have a vibration - motion starts sound energy
•Must have a medium – matter must transfer energy in
a wave
•Must have a receiver – vibrations must reach an ear
Light vs. Sound Waves
•Sound waves are mechanical waves
and require a medium
•Light waves are electromagnetic and
do not require a medium