SPI Reiview

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Author:
monkies
ID:
67978
Filename:
SPI Reiview
Updated:
2011-02-21 23:23:21
Tags:
Physics
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Description:
Edelman
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  1. what does an ellipse measure?
    area
  2. length
    cm, feet
  3. area
    cm^2, ft^2
  4. volume
    cm^3, ft^3
  5. percent
    is not a unit
  6. "increase by a factor of" means
    multiply
  7. decrease by a factor of means
    divide
  8. 10^9 = billion
    giga = G
  9. 10^6 = million
    mega = M
  10. 10^3 = thousand
    kilo = k
  11. 10^2 = hundred
    hecto = h
  12. 10^1 = ten
    deca = da
  13. 10^-1 = tenth
    deci = d
  14. 10^-2 = hundreth
    centi = c
  15. 10^-3 = thousandth
    milli = m
  16. 10^-6 = millionth
    micro = μ
  17. 10^-9 = billionth
    nano = n
  18. acoustic propagation properties
    the effects of the medium upon the sound wave
  19. biologic effect
    the effects of the sound wave upon the biologic tissue
  20. sound
    • a type of wave that carries enery, not matter from place to place
    • must travel through a medium
    • is mechanical, longitudinal wave
    • travels in a straight line
  21. compressions
    are areas of increased pressure or density
  22. rarefactions
    are areas of decreased pressure or density
  23. three acoustic variables
    • pressure = concentration of force w/i area force / area units= pascal (Pa)
    • density = concentration of mass w/i volume units = kg/cm^3
    • distance = measure of particle motion units = cm, ft, miles
  24. transverse wave
    particles move in a perpendicular direction (right angles or 90) to the direction of the wave
  25. sound is longitudinal wave
    particles move in the same direction as the wave
  26. acoustic parameters
    • period
    • fequency
    • amplitude
    • power
    • intensity
    • speed
    • wavelength
  27. period
    • the time required to complete a single cycle (the start of a cycle to the start of the next)
    • units = any unit of time
    • determines by = sound source
    • can not be changed by sonographer
  28. frequency
    • number of certain events that occure in a particular time duration
    • units = per second, 1/second = Herts (Hz)
    • determined = sound source
    • can not be changed by sonographer
    • frequency affects penetration and axial resolution
  29. ultrasound
    • a wave with a frequency exceeding 20,000Hz (20 kHz)
    • frequency is so high that is not audible
  30. audible sound
    heard by man, frequencies btwn 20Hz and 20,000Hz
  31. infrasound
    • sound with frequencies less than 20Hz
    • frequency is so low that is not audible
  32. frequency and period
    • are reciprocals
    • frequency (Hz) x period (sec) = 1
    • period (sec) = 1/ frequency (Hz)
    • frequency (Hz) = 1/period (sec)
    • when one goes down the other goes up
  33. Three bigness parameters
    • amplitude
    • power
    • intensity
  34. amplitude
    • the difference btwn the average value and the maximum value of an acoustic variable. the variation of an acoustic variable
    • units = same as acoustic variables
    • pressure=pascals
    • density=grams/cubic cm
    • particle motion=cm,inches,units of distance
    • may be expressed in decibels (dB)
    • determined by sound source (initially)
    • can be changed by sonographer
  35. power
    • the rate that work is performed, or the rate of energy transfer
    • units = watts
    • determined by sound source (initially)
    • can be changed by sonographer
  36. power & amplitude
    power is porportional to the wave's amplitude squared

    • ex: if amplitude is tripled, the power is increase by a factor of nine:
    • 3 x 3 = 9
  37. intensity
    the concentration of energy in a sound beam. the beam's power devided by the beam's cross-sectional area. intensity depends upon bothe the power and the cross-sectional area of the beam

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