C3: Partical Motion and Wave Propagation

Question 1

define acoustic propagation

Answer 1

-refers to the effects of tissue on sound

Question 2

define bioeffects

Answer 2

refers to the effects of sound of tissue

Question 3

what is sound

Answer 3

a propagating variation (eg wave)

Question 4

do sound waves carry energy or matter

Answer 4

energy

Question 5

do mechanical waves need a medium to travel

Answer 5

yes

Question 6

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

Answer 6

acoustic variables

Question 7

list the acoustic variables present when sound travels through a medium

Answer 7

• pressure
• density
• particle motion
• temperature

Question 8

describe pressure as an acoustic variable

how is it expressed?

Answer 8

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

Question 9

what is density

how is it expressed?

Answer 9

• 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

Question 10

describe the particle motion of longitudinal waves

Answer 10

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

Question 11

describe the particle motion of transverse waves

Answer 11

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

Question 12

what type of media can support transverse waves

Answer 12

only solids

Question 13

what type of media can support longitudinal waves

Answer 13

solids, liquids, gases

Question 14

what is mode conversion

Answer 14

when on type of wave is converted to another type

Question 15

what is frequency (f)

Answer 15

the number of cycles per second

in general: a measure of how often something occurs

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

Question 16

what is period (T)

Answer 16

the times it takes for one cycle to occur

Question 17

what is wavelength

Answer 17

the length of space one cycle takes up

Question 18

whats the avg speed of sound in soft tissue

Answer 18

1.54 mm/us or 1540 m/s

Question 19

what determines propagation speed

Answer 19

the medium

Question 20

what are the 3 ways to describe wave strength

Answer 20

amplitude

intensity

power
-total energy over the entire cross sectional area

Question 21

define amplitude

Answer 21

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

Question 22

define intensity

formula?

Answer 22

the [ ] of energy in a sound beam

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

Question 23

how is intensity related to amplitude

Answer 23

it is directly to amplitude^2

…. if you double the amp, you quadruple intensity

Question 24

is there any intensity during the listening phase?

Answer 24

no

Question 25

describe the changes of intensity throughout a pulse

Answer 25

intensity starts off high and gets weaker w/ time

Question 26

what is spatial avg and where do we measure it

Answer 26

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

Question 27

what is spatial peak and where is it found

Answer 27

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

Question 28

how are SA and SP related | formula?

Answer 28

the beam uniformity ratio BUR: SP/SA

Question 29

what is temporal peak (TP)

Answer 29

the greatest intensity found in the pulse

Question 30

what is pulse avg (PA)

Answer 30

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

Question 31

what is temporal avg (TA)

Answer 31

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

Question 32

do TP and PA have almost identical values

Answer 32

yes

Question 33

how are TP and TA related | formula?

Answer 33

by duty factor DF = TA/TP

Question 34

define duty factor

Answer 34

the % of time the crystal is ringing

Question 35

SPTA values depend on what factor

Answer 35

depth

Question 36

what is the speed of sound in fat

Answer 36

1460 m/s

Question 37

what is the speed of sound in bone

Answer 37

4080 m/s

Question 38

what is the range equation | what is it used for

Answer 38

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

Question 39

another name for SPTP and SPPA

Answer 39

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