Transcript Sound Wave Sound Waves

Sound Waves
Chapter 16
Old Riddle
 If
a tree falls in the middle of a
forest and no one is around,
does it make a sound?
Answer


To a scientist, the tree does make a sound no
matter whether someone hears it or not.
Sound- disturbance that travels through a
medium as a longitudinal wave
Sound Wave
Sound Waves


Sound Waves reflect, diffract
through narrow openings and
around barriers, and interfere
with each other
Reflection- sounds bounce
off surfaces such as walls

A reflected sound wave is called
an echo
Defraction

Why can you hear someone
in a classroom before you
enter the room?
Sound waves do not travel in
straight line
 They expand and contract to
fill the room which they are
entering

Interference

Interference- when waves interact with each
other
Constructive
 Destructive

Speed of Sound
If a sound wave is traveling through air at
room temperature, the speed of the wave is
343 m/s.
 The speed of sound depends on many
factors such as elasticity, density, and
temperature of the medium through which
it is traveling.
 Turn to pg 543. Look at the Math
Analyzing Data and do problems 1-3.

Elasticity

Elasticity- ability of a material to bounce
back after being disturbed
 Which
is more elastic?
 Modeling
clay
 Rubber band

The more elastic a medium, the faster the
sound travels.
 Solid-
more elastic
 Liquid- middle elastic
 Gas- Least elastic
Density
 Density-
how much matter that is in an
object
 In
an object with the same state (solid,
liquid, gas), sound travels slower in denser
object.
 Why?
 The
particles do not move as quickly in denser
object
Temperature

Temperature- how quickly
particles move
Sound travels more slowly in
lower temperatures
 Which wins? Put in order from
fastest to slowest.

30º C
 20º C
 10º C
 0º C

 Loudness-
Loudness
perception of energy of a
sound
 Loudness depends on two things: the
amount of energy it takes to make the
sound and the distance from the
source of the sound
 Shouting
vs. whispering
 The closer to a sound you are, the louder
 The
greater the energy used to
make the sound, the louder the
sound.
 Guitar
String- more energy used to
pick the string up, the louder it is.
The
more energy that is used, the
higher the amplitude.
 Loudness
increases as you get closer to
the origination of the sound.
 Why?
 The
closer you are to the origination of the
sound, the smaller the wave and the more
energy you hear.
 As a sound wave travels, the waves spread
and energy is also spread out.
Intensity
Intensity- the amount of energy a sound
waves carries per second through a unit
area
 A sound wave with a greater intensity,
sounds louder.
 As you walk away, it gets softer and
intensity goes down.

Decibels
 Loudness is measured in
decibels (dB)
 Loudness
of what we
can barely hear is 0dB
 30 dB is 3 times the level
of 10 dB
 Sounds louder than 100
dB can damage your ears
Pitch
 Pitch-
of a sound is a description
of how low or how high the sound
seems to a person
 Sound waves with a high frequency
has a high pitch.
 Sound waves with a low frequency
has a low pitch.




Female
(alto)
Male
(bass)
 We
can hear frequencies between 20
Hz and 2000 Hz
 Ultrasound- sound waves above the
normal hearing range
 Ultra-beyond
 Infrasound-
sound waves below the
normal human range of hearing
 Infra-
below
 When
singing, you change pitch
often.
 When you change pitch, you use
your vocal cords.
 Nestled in your vocal cords is your
voice box, which is called a larynx
 To
sing, you contract and relax
muscles in your throat and vocal
cords
Doppler Effect



The Doppler Effect- the change in frequency of
a wave as its source moves in relation to an
observer
The sound waves are a change frequency which
changes the pitch
When a sound source moves, the frequency of
waves changes because the motion of the source
adds to the motion of the waves

Ex. Tennis ball and wall- further you move back the
less the frequency
Groups of Instruments

Stringed- guitar and violin
Vibration when a string is strummed or plucked
 Pitch depends on length, thickness, material, and
how tightly its stretched


Wind- brass and woodwind
Vibrations against mouthpiece or reed
 Pitch depends on air column length


Percussion- drums, cymbals, and xylophones
Vibrate when struck
 Pitch depends on size, materials, and tension on
drumhead

Human Ear
 Function
of your ear is to gather
sound waves and send sound to your
brain.
 The outer ear funnels sound waves, the
middle ear transmits the waves inward,
and the inner ear converts sound
waves into a form that travels to your
brain
Outer Ear
 Outermost
ear looks and acts like a
funnel
 Ear canal- narrow region leading from
the outside of the human ear to the
eardrum
 Eardrum- small, tightly stretched,
drumlike membrane that vibrates
when sound enters
Middle Ear
 Behind
the eardrum, is the middle ear.
 Three smallest bones in your body
make up the middle ear: hammer,
anvil, and the stirrup
 Eardrum
causes the hammer to vibrate
 Hammer causes the anvil to vibrate
 Anvil causes the stirrup to vibrate
Inner Ear
The stirrup’s vibrations transfer to the
cochlea
 Cochlea- fluid filled sac shaped like a snail
shell
 On the cochlea are several hairs that sense
the vibrations and send the messages to the
brain through the auditory nerve

Echolocation
Echolocation- use of
reflected sound to
determine distances or to locate objects
 Animals use echolocation to find food and
avoid predators

 Bats
 Frequency
 Dolphins
around 100,000 Hz
Porpoises and Whales
 Frequencies
around 150,000
Ultrasound
 Ultrasound
technologies such as sonar
and ultrasound images are used to
observe things that cannot be seen
directly
 Sonar-Sound
Navigation and Ranging
 Used to determine depth of water, map
the ocean floor, and locate sunken ships
 Total
distance divided by two
Ultrasound
 Sonogram-
use of reflected ultrasound
waves to create a picture
 See
how many babies there are
 See sex of baby
 Position of a baby
 Diagnose and treat medical conditions