Basics Flashcards
Longitudinal wave:
particles of a medium are in a direction parallel to the wave propagation.
Mechanical wave:
a wave that requires a medium to travel
cannot propagate in a vacuum
Acoustic variable:
pressure, temperature, density, and particle motion (oscillation)
all of these variables change as an acoustic wave passes through a medium
The number of cycles per second:
freq
Unit for frequency:
MHz
Unit for period:
us
Unit for wavelength:
mm
What is propagation speed determined by?
density and stiffness
mm/us
Sound travels faster in lung than liver. True or false.
False– sound travels faster in stiffer material
If you double the frequency, what happens to the wavelength?
halves it
As imaging depth increase, what happens to the PRF?
decreases
What happens to the PRP when the imaging depth is increased?
increases
The max variation that occurs in an acoustic variable:
amplitude
Power relationship to amplitude?
power ∝ amplitude^
2
Units of intensity?
W/cm^2
Units for power?
Watts
Intensity relationship to amplitude?
Intensity ∝ amplitude^2
If amplitude doubles, then the intensity quadruples
Intensities in US range from?
1-50mW/cm^2
Intensities have both a peak value and an average value. The intensity of the sound beam as it
travels through a medium varies across the beam (spatial intensity) and with time (temporal
intensity).
Didn’t know this, thought it’d be good info to know lolz.
Spatial peak is the intensity where?
at the center of the beam
Spatial average is intensity where?
averaged throughout the beam
Temporal peak:
is the max intensity in the pulse
Temporal average:
intensity averaged over one of-off beam cycle.
takes into account the intensity at the beginning of one pulse to the beginning of the next
Pulse average:
intensity averaged over the duration of the single pulse
