Important

• what is a wave

  transfers energy

  rhythmic disturbance that travels through a medium
• what is compressions


  areas of high pressure and density
• what are rarefracitons 


  areas of low pressure and density
• what is sound


  travels in longitudinal mechanical waves
• what are the acoustic variables for sound

  pressure

  density

  distance
• what are the acoustic parameters

  frequency

  period

  wavelength

  propagation speed

  amplitude

  intensity

  power
• what is frequency 


  number of cycles per second
• what is a cycle

  one complete variation in pressure
• what unit is frequency

  Hertz
• what is infrasound level

  <20 Hz
• what is human hearing

  20-20,000 Hz
• what is ultrasound level

  >20,000 Hz
• what is period 


  amount of time for a single cycle
• what are the units for period

  seconds or microseconds
• what is the typical diagnostic ultrasound

  0.06 microseconds to 0.5 microseconds
• what is propagation speed

  how fast sound waves move through medium
• what are the units for propagation speed

  meters/second and millimeters/microseconds
• what is propagation speed determined by

  stiffness and density
• what is the average propagation speed for soft tissue

  1540 m/s or 1.54 mm/microseconds
• what is the propagation speed for air

  330
• what is the propagation speed for fat

  1450
• what is the propagation speed for water

  1480
• what is the propagation speed for blood

  1560
• what is the propagation speed for muscle

  1580
• what is the propagation speed for bone

  3500
• what is wavelength 


  amount of distance for a single cycle
• what is the unit for wavelength

  millimeters
• what is amplitude 


  max variation that occurs in an acoustic variable
• what is the unit for amplitude

  pascals
• what is clinical imaging for amplitude

  1mPa-2mPa
• what is power 


  rate at which work is performed
• what is the unit for power

  watts
• what is power determined by

  sound wave and medium
• what is intensity 


  concentration of energy

  rate at which energy passes through a unit area
• what are the units for intensity

  milliwatts per centimeter squared and W/cm^2
• what are harmonics 


  image from sound reflections at twice the frequency of transmitted sound
• how are harmonics frequencies generated 


  as sound travels through tissue
• how do higher pressure portions of wave travel

  faster than lower pressure portions
• what is pulse repetition frequency 


  number of pulses that occur in one second
• what is the unit for PRF

  kHz