Sound

  1. Define Intensity and state the units
    Normally, intensity _______ as you get farther from the source (explain and state the proportionality)
    • Intensity: the energy it transmits per second per unit area (i.e. power to area ratio)
    • Unit for intensity: W/m2
    • decreases 
    • Intensity decreases as the inverse square of the distance
    • Intensity ∝ 1/r2
  2. State the formula for Intensity 

    There are two types of areas, name and explain each
    • Intensity = power/area
    • Spread area: how much the source spreads out
    • Receiving area: the specific portion of the target being hit with a measured amount of light
  3. Label the diagarm
    State this diagram's formula for intensity
    The energy from the source is spread uniformly over a spherical surface area of _______. Intensity at distance r of a spherical wave from a source of ______ ______
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    • 4πr2
    • power Psource
  4. Define Loudness
    Loudness: a sensation in the consciousness of a human being and is related to a physically measurable quantity, the intensity of the wave
  5. Sound intensity levels are usually specified on a _______ scale 
    The unit on this scale is a _____, commonly the _______ (__)
    • logarithmic scale (base 10 log, not natural log)
    • bel
    • decibel (dB)
    • **10 dB = 1 bel
  6. State the formula for the sound level, β, of any sound in terms of intensity I: 

    Explain the denominator and state its value
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    • I0 is the intensity of a chosen reference level 
    • I0 = 1.0*10-12W/m2, this is the threshold of hearing, the lowest intensity the human ear can perceive
  7. Restate the sound level formula
    Every time we multiply by 10, we _____ _____ to β
    Every time we divide by 10, we _____ _____ from β
    Every time we double I, we _____ _____ from β
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    • add 10 
    • subtract 10
    • add 3
  8. Intensity is proportional to the square of the ______ _______. State the formula for Intensity (2) and the change in maximum pressure
    • wave amplitude 
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  12. When you hear the sound of the siren, can you tell any difference if it is approaching or receding from you?
    If so, identify the phenomena at play
    • You should hear different frequency. The perceived frequency of the siren travels toward you is higher than when it moves away
    • The Doppler Effect
  13. When is the Doppler Effect experienced (for sound)
    When the motion of the source or observer is toward the other (converging on the other), the frequency appears to _______. When the motion of the source or observer is away from the other (diverging from the other), the frequency appears to ________
    • Doppler Effect, for sound, is experienced whenever there is relative motion between the source and the observer
    • increase 
    • decrease
  14. Consider an observer moving toward a point source with speed v0. The source remains stationary relative to the air. The waves are represented with a series of circular arcs concentric to the source. The surface of each circle is the ________.
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    wavefront
  15. The dots are the positions of the source at t = 0, T, 2T, and 3T. The source emits ________, (__). 
    **Note the speed of the source
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    • frequency, (f0)
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  16. Snapshot at time 3T
    What happens to the wavelength behind the source?
    What happens to the wavelength in front of the source?
    From crest 0-2, state the time, and the point on which the wave front (circle) is centered
     
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    • expanded to λ-
    • compressed to λ+
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  17. Case 1: Source moving at speed νs
    Wave is either compressed or spread out, depends on if the source is moving toward or away from the listener. State the formula for the new wavelength, λ' (2). The difference in wavelength is due to the distance covered by the ______, (__). State the formula for the frequency at that new wavelength, f'. 
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    • source, (νs/f)
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  18. Case 2: Listener is moving at speed v0
    The listener will think the sound travels at a ______ speed 
    The relative speed is due to the speed of the _____, thus
    νrel = ___ + ___
    What is the formula for the corresponding frequency?
    • different speed
    • listener 
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  19. General Case
    Source moves at speed ____ and the listener moves at speed ____
    Combining the 2 cases
    f' = ______ = ______ = ______
    Don't forget that the velocity is a ______, i.e. depend on its direction. This is the case for when both source and listener are ________ each other. What changes when this isn't the case?
    • Source moves at vs
    • Listener moves at v0
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    • vector
    • approaching 
    • **Use correct sign when applying the formula:
    • When source and listener are diverging:
    • f' = fdoppler = vrel/λ' = fsource[(v -v0)/(v+vs)]
  20. State the formula for frequency as it pertains to the Doppler Effect
    Convenient rules for signs:
    The word toward is associated with an _______ in the observed frequency
    The words away from are associated with a _______ in the observed frequency
    The motion of the source cause the wavelength to ______. What does the motion of the listener change? The ______ effect is common to all waves
    • f = ν/λ
    • increase
    • decrease
    • change
    • changes the relative wave speed of the sound 
    • The Doppler effect
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  22. Application of Doppler Shift in Medical Field
    If we send a pulse of frequency f toward a moving object, such as a beating heart. Suppose the heart valve moves away from the source with speed v. What can the Doppler shift technique tell you? 
    Also, how can the ultrasound imaging help you locate an object?
    Bats can use the Doppler effect to detect the ______ of insects
    State two things Doppler Sonography can be used for
    • You can tell how fast the heart valve is moving 
    • Can help you to locate an object by the time delay of the reflected pulse
    • motion
    • Doppler Sonography can be used to measure the speed of blood in arteries and detect turbulence in blood flow
  23. Since there is no _______ required for light waves, only the _______ ______, (__), between the source and the observer can be identified
    • medium 
    • relative speed, (v)
  24. The Doppler effect is used to measure shifts in the _______ of light emitted by a moving astronomical object such as a galaxy. Light emitted by atoms in other galaxies are shifted toward the _____ end of the spectrum (i.e. ____ shifted). This indicates that these galaxies are _______ from us (explain). Similarly, light from an approaching source is ______ shifted (detected wavelengths are ______ than the emitted wavelengths).
    • frequency
    • red end 
    • Red shifted
    • receding aka The Universe is expanding
    • blue shifted 
    • shorter
  25. If a light source is receding from the observer with relative speed v, what is the formula for frequency f' measured by the observer:
    What is the formula for the new wavelength λ':
    The color is shifted towards the _____ end of the visible spectrum, thus we call this effect _____ shifted
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    • red end 
    • red shifted
  26. If a light source is approaching the observer with relative speed v, what is the formula for the frequency f' measured by the observer:
    What is the formula for the new wavelength λ':
    The color is shifted towards the _____ end of the visible spectrum, thus we call this effect ______ shifted
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    • blue end
    • blue shifted
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Author
chikeokjr
ID
345343
Card Set
Sound
Description
Sound
Updated