Dmitri Shostakovich
(1906-1975)
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Symphony No. 5
Last Movement (1937). |
Introduction
Waves
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A wave is an array of neighboring objects oscillating in a regular,
progressive manner relative to one another. |
Displacement vs. Position
Displacement vs. Time
Terminology
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Frequency |
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Number of oscillations per second |
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Wavelength |
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Distance between adjacent crests |
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Amplitude |
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Maximum displacement |
Slide 7
Types of Waves
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Transverse Wave |
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Particles oscillate perpendicular to
the direction in which the wave moves |
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Longitudinal Wave |
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Particles oscillate parallel to the
direction in which the wave moves |
Waves
(Alternate
Definition)
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A wave is a disturbance traveling
outward from a vibrating source. |
Sound Waves
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Produced by oscillating air molecules |
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Longitudinal waves |
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Periodic pressure variations are set up |
Sound Waves
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The actual motion is molecular
(microscopic). Difficult to measure
and visualize. |
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The pressure changes are
macroscopic. Easy to measure and
visualize. |
Sound Waves
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(1) When the pulse reaches a particular point, the pressure
increases from normal atmospheric pressure to some maximum value. |
Sound Waves
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(2) As the pulse continues to move through the point, the
pressure begins to return to normal atmospheric pressure. |
Sound Waves
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(3) As the trailing edge of the pulse approaches, the pressure
falls below normal atmospheric pressure. |
Sound Waves
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(4) When the pulse has passed, the
pressure returns to normal atmospheric pressure. |
Sound Waves
(Pressure
Variations)
Pressure vs.
Position
(at a fixed time)
Pressure vs. Time
(at
a fixed point)
Sound Waves
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A sound wave is a longitudinal wave
with a frequency between 20 Hz and 20,000 Hz. |
Sound Waves
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The frequency of a sound wave is always
the same as the frequency of the vibrating source that produces it. |
Sound Waves
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frequencies < 20 Hz
INFRASOUND |
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frequencies > 20,000 Hz
ULTRASOUND |
Velocity of Sound Waves
Velocity of Sound Waves
Velocity of Sound Waves
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The velocity of any wave is directly proportional to the square root
of the stiffness factor and inversely proportional to the square root of the
inertia factor. |
Speed of Sound in Air
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The speed of sound in air is: |
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344 meters per second |
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1030 feet per second |
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770 miles per hour |
Effect of Temperature on
Speed of Sound
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The speed of sound changes by 0.6 m/s for every 1 degree change in the
Celsius temperature. |
Effect of Temperature on
Speed of Sound
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If the temperature increases, the speed
of sound increases. |
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If the temperature decreases, the speed
of sound decreases. |
Energy In Sound Waves
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Kinetic and Potential Energy |
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Larger Amplitude means more energy = louder |
Relation Among Velocity,
Frequency, and Wavelength
Physical/Perceived
Musical Characteristics
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Physical Perceived |
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Characteristic Characteristic |
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Frequency Pitch |
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Amplitude Loudness |
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Waveform Timbre |