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Sound

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Title: Sound


1
Sound
  • Chapter 16

2
Nature of Sound
  • Sound is a disturbance that travels through a
    medium as a longitudinal wave.
  • Sound is a mechanical wave because it requires a
    medium

3
Speed of Sound
  • The speed of sound is 346 m/s at room
    temperature.
  • The speed of sound depends on elasticity,
    density, and temperature of the medium.

4
Speed of Sound
  • Elasticity is the ability of a material to bounce
    back after being disturbed.
  • Density is the amount of matter in a given
    volume.
  • Temperature is a measure of the average kinetic
    energy.

5
Speed of Sound
  • Sound travels more quickly in mediums that have a
    high degree of elasticity.
  • Sound travels more slowly in denser materials.
  • Sound travels more slowly at a lower temperature
    and faster at higher temperature.

6
Energy is required to create a sound wave. Sound
energy is also known as . . .
  • Elastic potential energy
  • Radiant energy
  • Acoustic energy
  • Thermal energy

7
Properties of Sound
  • Intensity of a sound wave is the amount of energy
    that a wave carries per second through a unit
    area.
  • Loudness describes what you actually hear.
  • A sound wave of greater intensity generally sound
    louder.

8
Sound Loudness
  • The loudness of sound is measured in decibels.
  • Threshold of hearing is at 0 decibels.
  • Sound louder than 120 decibels can cause pain and
    permanent damage.

9
Frequency Pitch
  • Frequency is the number of sound waves that pass
    a given point in a given amount of time.
  • Human hearing is between 20 Hz and 20,000 Hz.
  • Ultrasound is sound waves above the normal human
    hearing range.

10
Frequency Pitch
  • Infrasound are sound waves that are below the
    normal range of human hearing.
  • Pitch of a sound is a description of how high or
    low the sound seems to a person.
  • Pitch of a sound that you hear depends on the
    frequency of the sound wave.

11
As the frequency of a sound wave increases . . . .
  • Pitch increases.
  • Pitch decreases.
  • Pitch stays the same.
  • HELP! I dont get it!

12
Resonance
  • Resonance occurs when the frequency of the sound
    waves and the natural frequency of the objects
    are the same.
  • If resonance occurs in an object that is not
    flexible, the object will break (shattering of a
    glass).

13
The Doppler Effect
  • The apparent change in frequency as a wave source
    moves in relation to the listener is called the
    Doppler Effect.
  • As sound source moves toward the listener, the
    waves reach the listener with a higher frequency.
  • The pitch appears to increase because of the
    Doppler effect.

14
Combining Sound Waves
  • Timbre describes the quality of the sound you
    hear.
  • The blending of the fundamental tone and the
    overtones makes up the characteristic sound
    quality, or timbre, of a particular sound.

15
Music
  • Music is a set of tones combined in ways that are
    pleasing to the ear.
  • Types of instruments
  • Strings
  • Brass
  • Woodwinds
  • Percussion

16
Noise
  • Noise has no pleasing timbre and no identifiable
    pitch.

17
Interference of Sound Waves
  • Interference occurs when two or more sound waves
    interact.
  • Acoustics describe how well sound can be heard in
    a particular room or hall.
  • Repeated change in loudness are called beats.

18
Hearing Sound
  • The outer ear funnels sound waves, the middle ear
    transmits the waves inward, and the inner ear
    converts the sound waves into a form that your
    brain can understand.

19
Outer Ear
  • The outer ear funnels the sound waves to the ear
    canal.
  • The sound travels down the ear canal and vibrates
    the eardrum.

20
Middle Ear
  • The middle ear contains three small bones
    hammer, anvil and stirrup.
  • The vibrations travel from the eardrum to the
    hammer, then the anvil and finally the stirrup.

21
Inner Ear
  • The stirrup vibrates the cochlea.
  • The cochlea contains fluid and tiny hairs that
    are stimulated by the vibrations.
  • The stimulations of the tiny hairs send messages
    to the brain.

22
Hearing Loss
  • Hearing loss is caused by
  • Injury
  • Infection
  • Aging (like me?)

23
Facts
  • More than 40 million Americans have hearing loss.
  • Approximately 40 of the hearing-impaired are
    under age 65.
  • About 2 million children under age 18 are
    hearing-impaired in the U.S.
  • Minor decreases in hearing, especially of higher
    frequencies, are normal after age 20.
  • Some form of hearing loss affects 1 out of 5
    people by age 55.

24
Facts
  • One-third of Americans between the ages of 65 and
    74 - and one-half of those age 85 and older -
    have some form of hearing loss.
  • Hearing loss is the third leading chronic
    disability, following arthritis and high blood
    pressure.
  • Between 7 and 10 million people in American
    industry have noise-induced hearing loss,
    virtually all of which was preventable.
  • About 15 of college graduates have a level of
    hearing loss equal to or greater than their
    parents a significant cause is listening to loud
    music.

25
Facts
  • In the U.S., 12 million people have hearing aids.
  • Of the 12 million with hearing aids, only 6
    million actually wear them eight hours a day,
    seven days a week.

26
Application of Sound
  • An echo is a reflected sound wave.
  • Some surfaces absorb sound waves.
  • Other surfaces reflect sound waves

27
Sonar
  • Sonar is a system of detecting reflected sound
    waves.
  • Sonar stands for sound navigation and ranging.
  • A sonar device measures the time it takes to
    detect the reflected sound waves.

28
Ultrasound
  • Ultrasonic frequency is sound waves above 20,000
    Hz.
  • Echolocation is the use of sound waves to
    determine distance or to locate objects.
  • Bats use echolocation to navigate and to find
    food.

29
Ultrasound (continue)
  • Ultrasound produce pictures called sonogram.
  • Doctors use ultrasound to look inside the human
    body and to diagnose and treat medical
    conditions.
  • Ultrasound is used for focusing cameras, brushing
    teeth and cleaning jewelry.

30
Test
  • This Tuesday/Wednesday, March 3rd/4th.
  • Covers all of sound waves in chapter 16.

31
Review Questions
  • What type of wave is sound?
  • (longitudinal)
  • What are three factors that affect the speed of
    sound?
  • (elasticity, density temperature)
  • What are the three bones in the middle ear?
  • (hammer, anvil stirrup)
  • Is sound faster in warmer or cooler temperatures?
  • (warmer)

32
Review Questions
  • Is sound faster in elastic material or material
    that is not elastic?
  • (elastic)
  • Is sound faster in less dense or more dense
    medium?
  • (less dense)
  • What does the stirrup shake in the middle ear?
  • (cochlea)
  • What does sonar stand for?
  • (sound navigating and ranging)

33
Review Questions
  • How do bats navigate?
  • (echolocation)
  • What effect describes an increasing pitch as a
    loud noise is approaching and decreasing pitch as
    a loud noise is moving away?
  • (Doppler Effect)
  • What is the property of sound that is described
    as the amount of energy that passes by a point
    each second?
  • (intensity)
  • How loud or soft noise is appears to be is known
    as ___________.
  • (pitch)

34
Review Questions
  • What you hear is known as _______________.
  • (loudness)
  • Sound is measured in ________________.
  • (decibels)
  • Sound waves with frequencies below the human
    range of hearing is known as _______________.
  • (infrasound)
  • Sound waves with frequencies above the human
    range of hearing is known as _______________.
  • (ultrasound)

35
Review Questions
  • When the frequency of an object and the natural
    frequency are the same, it is known as
    _______________.
  • (resonance)
  • _______________ describes the quality of sound.
  • (timbre)
  • What group of instrument vibrates the lips to
    produce sound?
  • (brass)
  • What group of instruments vibrates a reed to
    produce sound?
  • (wood-wind)

36
Review Questions
  • What group of instruments produces sound by
    rubbing, plucking or striking a string?
  • (string)
  • What group of instruments produces sound by being
    struck?
  • (percussions)
  • Sound with no identifiable pitch and unpleasing
    to the ear is known as _______________.
  • (noise)
  • Sound pleasing to the ear with an identifiable
    pitch is known as _______________.
  • (music)

37
Review Questions
  • _______________ describes how well sound can be
    heard in a particular room.
  • (acoustics).
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