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- Sound waves are pressure fluctuations, ccreated by a vibrating source.
- Sound waves are longitudinal waves, prodduced by the compression and rarefaction of particles in a medium.
- The wavelength is the distance between aadjacent regions of maximum compression.
- The frequency of a sound wave is heard aas pitch.
- An average human can only hear sound wavves that range between 20 Hz and 20,000 Hz.
- The notes of the musical scale have diffferent frequencies.
- The amplitude of a sound wave is heard aas loudness.
- The velocity of sound in air depends on temperature.
331 m/s at 0o C
343 m/s at 20o C
366 m/s at 100o C
- The velocity of sounds in liquids and soolids is faster than in gases. (page 482)
- Sound waves do not travel in a vacuum.
- The equation that relates velocity, freqquency, and wavelength is:
v = f λ
- When a sound wave enters a different meddium, the frequency of the wave remains constant while the wavelength changes.
- The Doppler Effect is a sudden shift in a wave's perceived frequency when there is relative motion between a source and a listener.
- The Doppler shift causes sounds to seem higher in frequency when the sound source is moving toward the listener, and lower in frequency when the source is moving away from the listener.
- The Doppler Effect can be determined usiing the equation:
f L | = | f S
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(
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V + VL
V - VS
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)
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- In the above formula v is the speed of ssound in air. The velocity of the listener, vL, is positive when moving towards the source and negative when moving away from the source. The velocity of the source, vS, is positive when moving towards the listener and negative when moving away from the listener.
- The Doppler Effect occurs with light wavves also. This is used in astronomy to determine whether a star or galaxy is moving towards or away from our galaxy.
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