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Ultrasound Physics > Interaction of Sound and Media > Flashcards

Interaction of Sound and Media Flashcards

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1
Q

as sound waves propagate, what happens to attenuation

A

it increases

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2
Q

term describing weakening of sound waves as they travel in media

A

attenuation

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3
Q

decibel notation is described as ___ because it reports relative changes in signal strength

A

logarithmic

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4
Q

effect of 3dB

A

doubles

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5
Q

effect of 6dB

A

4x

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6
Q

effect of 9dB

A

8x

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7
Q

effect of 10dB

A

10x

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8
Q

effect of 20dB

A

100x

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9
Q

effect of -20dB

A

1/100

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10
Q

effect of -10dB

A

1/10

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11
Q

effect of 9dB

A

1/8

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12
Q

effect of 6dB

A

1/4

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13
Q

effect of -3dB

A

1/2

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14
Q

Sound waves weaken as they propagate. This decrease in intensity, power, and amplitude as sound travels is called

A

attenuation

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15
Q

attenuation is determined by 2 factors

A

path length

frequency

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16
Q

how are distance and attenuation related

A

directly

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17
Q

how are frequency and attenuation related

A

directly

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18
Q

3 processes that contribute to attenuation

A

reflection
scattering
absorption

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19
Q

as sound strikes a boundary, a portion of the wave’s energy may be redirected, or __

A

reflected

20
Q

two forms of reflection

A

specular

diffuse / backscatter

21
Q

type of reflection that happens when it hits a smooth boundary and the sound is reflected in only one direction, in an organized manner

A

specular

22
Q

type of reflection that happens when a wave reflects off an irregular surface and radiates in more than one direction

A

diffuse reflection or backscatter

23
Q

random redirection of sound in many directions is called

A

scattering

24
Q

how is scattering related to frequency

A

directly

25
Q

do high frequency sound beams scatter more or less than low frequency beams?

A

high frequency beams scatter more

26
Q

A special form of scattering that occurs when the structures dimensions are much smaller than the beams wavelength. (redirects sound wave equally in all directions)

A

Rayleigh scattering

27
Q

Rayleigh scattering relationship with frequency

A

Rayleigh scattering is directly proportional to frequency^4

28
Q

___ occurs when ultrasonic energy is converted into another energy form such as heat

A

absorption

29
Q

attenuation coefficient formula

A

frequency (MHz) / 2 = atten. coeff. (dB / cm)

30
Q

total attenuation formula

A

total atten. (dB) = atten. coeff. (dB/cm) x distance (cm)

31
Q

Media in which attenuation is the highest

A

air

32
Q

media in which attenuation is the lowest

A

water

33
Q

the distance sound travels in a tissue that reduces the intensity of sound one-half its original value

A

half value layer thickness
penetration depth
half boundary layer

34
Q

half-value layer thickness depends on 2 factors

A

medium

frequency

35
Q

acoustic resistance to sound traveling in a medium

A

impedance

36
Q

how do we calculate impedance

A

impedance (rayls, Z) = density (kg/m3) x propagation speed (m/s)

37
Q

normal incidence is also called

A

perpendicular
orthogonal
right angle
90 degrees

38
Q

oblique incidence occurs at the incident sound beam strikes a boundary at what angle

A

any angle other than 90 degees

39
Q

units for intensity

A

w/cm2

40
Q

intensity of the portion of the incident intensity AFTER striking a boundary

A

transmitted intensity

41
Q

sound waves intensity BEFORE striking a boundary is called

A

incident intensity

42
Q

conservation of energy equations

A

incident intensity = reflected intensity + transmitted intensity
100% = IRC% + ITC%

43
Q

what happens when there is a change in impedances between media

A

reflection

44
Q

at an oblique incidence, these two things are always true

A

conservation of energy

incident angle = reflection angle

45
Q

change in direction of a wave propagation when traveling from one medium to another

A

refraction

46
Q

refraction occurs only under two conditions…

A

oblique incidence

different propagation speeds between 2 media

Ultrasound Physics (24 decks)

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