Intensity Determines Loudness

1
Intensity Determines Loudness

• Sect. 16-3

2
How is Amplitude Related to Loudness? Pg 533

• How did the loudness of the sounds compare?
• How is amplitude related to loudness?
• Challenge Using what you learned from
  experimenting with the rubber band, explain why
  swinging a drumstick harder on a drum would make
  a louder sound than swinging a drumstick lightly.

3
Intensity determines loudness.
16.3
A sound wave with a lower amplitude and energy
is perceived as a softer sound.
intensity
decibel
amplification
acoustics
CHAPTER RESOURCES
SECTION OUTLINE
4
Intensity determines loudness.
16.3
A sound wave with a higher amplitude and energy
is perceived as a louder sound.
intensity
decibel
amplification
acoustics
CHAPTER RESOURCES
SECTION OUTLINE
5
Intensity determines loudness.
16.3
intensity
A sound wave with a higher amplitude and energy
is perceived as a louder sound.
decibel
amplification
acoustics
CHAPTER RESOURCES
SECTION OUTLINE
6
intensity
16.3
Intensity determines loudness.
intensity
decibel
The amount of energy of a wave, per wavelength.
Intensity is associated with the amplitude of a
sound wave and with the quality of loudness
produced by the sound wave.
amplification
acoustics
CHAPTER RESOURCES
KEY CONCEPT SUMMARY
7
The more energy a sound wave carries, the more
intense it is and the louder it will sound.

• The intensity of a sound is the amount of energy
  its sound wave has.
• A unit called the decibel(dB) is used to measure
  sound intensity
• Amplitude is also a measure of wave energy The
  greater the amplitude, the more intensity a sound
  wave has and the louder the sound will be.

8
Approximate Sound Intensities pg. 534

• At more than 100 decibels sounds become very
  loud.
• What is the source of the most intense sound in
  the picture?
• What is the source of the least intense sound in
  the picture?

9
Why is it harder to hear a person talking far
away from you than someone who is closer to you?

• Sound waves spread out from their source in all
  directions. As they spread out, their energy
  spreads out, so the loudness decreases.

10
decibel
16.3
Intensity determines loudness.
intensity
decibel
dB The unit used to measure the intensity of a
sound wave.
amplification
acoustics
CHAPTER RESOURCES
KEY CONCEPT SUMMARY
11
Controlling the Intensity of Sound

• As the amplitude of a sound decreases, the
  frequency stays the same.
• Change intensity without changing its quality by
  taking energy away from or adding energy to a
  sound wave.
• Sound intensity can be controlled in many ways.
  Ex) muffler

12
amplification
16.3
Intensity determines loudness.
intensity
decibel
The strengthening of an electrical signal, often
used to increase the intensity of a sound wave.
amplification
acoustics
CHAPTER RESOURCES
KEY CONCEPT SUMMARY
13
Amplification

• Increases the strength of an electrical signal.
• Often used to increase the intensity of a sound
  wave.
• Experienced when you listen to a t.v., radio, or
  stereo.

14
Amplification

• When the frequency of an applied force matches
  the natural frequency of a system, large
  amplitude vibrations results in whats called
  resonance.
• Resonance explains why a glass shatters at a
  pitch that matches its natural frequency.

15
Amplification in a Stereo

• Sound input comes from a microphone in the form
  of weak electrical signals
• Transistors turn these signals into stronger
  ones, which are converted into vibrations in a
  coil in the speakers.
• The coil is attached to a cone, which vibrates
  and sends out sound waves.

16
Acoustics
16.3
Intensity determines loudness.
intensity
decibel
The scientific study of sound the behavior of
sound waves inside a space.
amplification
acoustics
CHAPTER RESOURCES
KEY CONCEPT SUMMARY
17
Acoustics

• Involves how sound is produced
• Involves how sound is received and heard
• Refers to the way sound waves behave inside a
  space.

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Compare and Contrast p.535

• Imagine sound waves reflecting off the surfaces
  in the two photographs.
• How do the reflections differ?
• How would the addition of sound absorbing
  materials affect sound?

19
Intense sound can damage hearing

• Damage and destroy the hair cells inside the ear
• Ear damage can be lessened by wearing ear
  protection, such as ear plugs, or by covering the
  ears.
• If the damage is slight, injured cells might be
  repaired, but such delicate cells could be
  permanently damaged.

20
Sound has many uses.
16.4
echolocation
16-4 Human uses of sound
sonar
sonar
ultrasound
music
telephone
recording
CHAPTER RESOURCES
SECTION OUTLINE
21
Sound has many uses.
16.4
echolocation
sonar
Bats use sound to locate objects.
CHAPTER RESOURCES
SECTION OUTLINE
22
Objects that can be detected by ultrasound

• Food sources
• Objects underwater
• Inside of the body

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Echolocation

• Sending out of ultrasound waves and interpreting
  the returning echo.
• Bats use sound to locate objects

24
Explore Echoes

• How did sound change when you added the book?
• How can an echo be used to detect an object?

25
Explore Echoes

• How did sound change when you added the book?
  The sound was louder with the book than without
  the book.
• How can an echo be used to detect an object? An
  echo can be used to detect an object by
  reflecting off the object. If there is no object
  to reflect off, there would be no echo.

26
Sonar

• Instruments that use echolocation to locate
  objects
• Stands for sound navigation and ranging
• Can detect sounds from submarine propellers

• Can locate underwater objects
• Can find schools of fish
• Can be used to map the ocean floor
• Can be used to find sunken ships

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Ultrasound can be safely used on humans

• Ultrasound waves cannot be heard by humans, so
  they can be used on humans at very high
  intensities without damaging hearing.

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Medical Uses of Ultrasound

• Examine internal organs
• Check the health of a fetus during pregnancy.
• Can break up kidney stones

29
Sound waves can produce music Characteristic
sounds of instruments

• All of the pitches of the instrument, along with
  the resonance of the instrument itself, produce
  the characteristic sound of the instrument.

30
Changing the pitch of a drum

• Loosen or tighten the drum skin

31
While playing a particularly long and loud song
on your guitar, it may become out of tune.

• What has happened is that the strings have
  loosened and the pitch has changed.

32
Two inventions in the late 1800s that changed the
world of sound

• Telephone
• phonograph

33
How telephones transmit your voice to another
telephone

• As you speak into the mouthpiece, your sound
  waves cause a thin disk inside to vibrate.
• A microphone turns these vibrations into
  electrical signals.
• These signals are sent over wire to a switching
  station.
• Computers connect the wire to the other telephone.

34
How Edisons Phonograph machine worked

• Edisons phonograph had a needle connected to a
  diaphragm that could pick up sound waves.
• The vibrations of the sound waves were sent to
  the needle, which cut into a piece of foil.
• To play back the sound, Edison used another
  needle to track along the grooves made in the
  foil.