Transcript Section 4 Powerpoint

Section 4
Sound and Hearing
Properties of Sound Waves
• Sound waves are longitudinal waves —
compressions and rarefactions that travel
through a medium.
• Many behaviors of sound can be
explained using a few properties—
speed, intensity and loudness, and
frequency and pitch.
Speed of Sound
• Speed of a wave depends on the medium
it travels in
• The speed of sound is determined by the
temperature, elasticity, and density of the
medium through which the sound travels.
Speed of Sound
• Temperature:
• Low temperatures makes the medium vibrate
slower, Hence slowing the speed of sound
• Elasticity:
• Solids are generally more elastic than liquids
and liquids are generally more elastic than
gases
• Density:
• If the medium is the same, the speed of sound is
slower the more dense it is.
Intensity and Loudness
• The amount of energy carried by a wave in
a certain amount of time
• Intensity determines the loudness of a
sound
• Intensity scale is measured in the unit
Decibel (dB)
Over 140 dB is painful for humans
Instant Perforation of Eardrum 160 dB
Frequency and Pitch
• Pitch:
• A description of a sound as high or low
• The pitch of a sound wave is determined
by how the number of waves produced in
a given time (Frequency)
• Thus the pitch of a sound depends on the
frequency of waves
Frequency and Pitch
• Humans can hear from about 20 to 20,000
hertz
• Sounds higher than 20,000 hertz are
known as Ultrasonic
• Sounds lower than 20 hertz are known as
Infrasonic
Doppler Effect
• Occurs whenever there is motion between
the source of a sound and its receiver
Link
If you are in front of the source the frequency is
higher hence producing a higher pitch sound
If you are behind the source the frequency is lower,
hence producing a lower pitch sound
Doppler Effect
Sound Uses
• Sound has many applications in the
medical field, cleaning, and locating
objects.
Sonar
• Sound Navigation and Ranging
• High frequency ultrasonic waves used to see
using sound.
• Research ships use this to find sunken ships.
• The Navy used it to map all of the worlds
oceans, submarines use it to see, and
battleships use it to find subs.
• Fishing boats use it to find fish.
• Cameras use it to automatically focus.
Images from SONAR
• Fish
• USS Utah
• Volcano on the sea floor
Ultrasonic Cleansing
• Used on objects that are too delicate to
clean with sponges
• Jewelry, electronic components, delicate
machine parts.
• Teeth are also cleaned ultrasonically
Ultrasonic Cleansing
Sound and Medicine
• Used to diagnose medical problems
• Used as an X-ray
• Used to take pictures of babies
(Ultrasound)
• Used to destroy calcium build-ups in the
body (kidney stones, gall stones)
Ultrasound Images
Kidney
Stone
It works
like this!!
The Ear
• In humans, the organ of the body that
detects sound is the ear.
• There are three parts to the human ear
• Outer
• Middle
• Inner
Outer Ear
• The outer ear acts a funnel for the sound
waves entering the ear
• The sound waves are moved down the ear
canal to the Eardrum (a lightly stretched
membrane) Link
• The ear canal has wax in it to keep the
eardrum moist
Middle Ear
• Contains the three smallest bones in the
human body
• The Hammer – picks up the vibrations
from the eardrum
• The Anvil – gets the vibrations from the
hammer and transmits them to
• The Stirrup – it transmits its vibrations to
another membrane
Inner Ear
• The vibrations are channeled into the
Cochlea
• Cochlea – shaped like a snail shell
contains a liquid and hundreds of cells
connected to nerve fibers.
• These nerve fibers form one nerve that
send impulses to the brain where it is
interpreted as sound
Cochlea
How The Ear Works
Reviewing Concepts
• 1. List five properties used to explain the
behavior of sound waves.
• 2. Name two uses for ultrasound.
• 3. What is the Doppler effect?
• 4. What are the ear’s three main regions?
Describe the function of each region.