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Physics 1 > C3: Partical Motion and Wave Propagation > Flashcards

C3: Partical Motion and Wave Propagation Flashcards

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1
Q

define acoustic propagation

A

-refers to the effects of tissue on sound

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2
Q

define bioeffects

A

refers to the effects of sound of tissue

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3
Q

what is sound

A

a propagating variation (eg wave)

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4
Q

do sound waves carry energy or matter

A

energy

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5
Q

do mechanical waves need a medium to travel

A

yes

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6
Q

whats the term that refers to the quality of a sound wave

A

acoustic variables

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7
Q

list the acoustic variables present when sound travels through a medium

A
  • pressure
  • density
  • particle motion
  • temperature
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8
Q

describe pressure as an acoustic variable

how is it expressed?

A

pressure is expressed as a sine wave…. crests represent high pressure and troughs represent low pressure

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9
Q

what is density

how is it expressed?

A
  • the concentration of particles or mass per unit volume
  • with reference to a sine wave… areas of high density (crests) are called compressions and areas of low density (troughs) are called rarefractions
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10
Q

describe the particle motion of longitudinal waves

A

back and fourth motion, parallel to the direction of travel of the wave

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11
Q

describe the particle motion of transverse waves

A

up and down motion, perpendicular to the direction of travel of the wave

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12
Q

what type of media can support transverse waves

A

only solids

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13
Q

what type of media can support longitudinal waves

A

solids, liquids, gases

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14
Q

what is mode conversion

A

when on type of wave is converted to another type

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15
Q

what is frequency (f)

A

the number of cycles per second

in general: a measure of how often something occurs

formula: f = 1/T or f = c/lambda

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16
Q

what is period (T)

A

the times it takes for one cycle to occur

17
Q

what is wavelength

A

the length of space one cycle takes up

18
Q

whats the avg speed of sound in soft tissue

A

1.54 mm/us or 1540 m/s

19
Q

what determines propagation speed

A

the medium

20
Q

what are the 3 ways to describe wave strength

A

amplitude

intensity

power
-total energy over the entire cross sectional area

21
Q

define amplitude

A

max. variation of an acoustic variable… strength of the wave is determined by the source of the sound

22
Q

define intensity

formula?

A

the [ ] of energy in a sound beam

formula:
I = P/A (power over area)

23
Q

how is intensity related to amplitude

A

it is directly to amplitude^2

…. if you double the amp, you quadruple intensity

24
Q

is there any intensity during the listening phase?

A

no

25
Q

describe the changes of intensity throughout a pulse

A

intensity starts off high and gets weaker w/ time

26
Q

what is spatial avg and where do we measure it

A

SA is the avg intensity over the entire beam… measured at the face of the probe

27
Q

what is spatial peak and where is it found

A

SP is the peak intensity of the beam, found at the focal point where the beam is the skinniest

28
Q

how are SA and SP related

formula?

A

the beam uniformity ratio

BUR: SP/SA

29
Q

what is temporal peak (TP)

A

the greatest intensity found in the pulse

30
Q

what is pulse avg (PA)

A

avg value for all intensities found in a pulse excluding dead time

31
Q

what is temporal avg (TA)

A

avg value for all intensities found in a pulse INCLUDING dead time b/w pulses

32
Q

do TP and PA have almost identical values

A

yes

33
Q

how are TP and TA related

formula?

A

by duty factor

DF = TA/TP

34
Q

define duty factor

A

the % of time the crystal is ringing

35
Q

SPTA values depend on what factor

A

depth

36
Q

what is the speed of sound in fat

A

1460 m/s

37
Q

what is the speed of sound in bone

A

4080 m/s

38
Q

what is the range equation

what is it used for

A

D = C x t

D= distance to reflector and back
c = speed of sound
t = time for round trip

used to calculate the distance of a reflector from the probe

39
Q

another name for SPTP and SPPA

A 
SPTP = instantaneous peak
SPPA = maximum intensity or time averaged half maximum

Physics 1 (7 decks)

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