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Physics > Interaction Of Sound And Media > Flashcards

Interaction Of Sound And Media Flashcards

1
Q

What is a logarithm?

A

A novel method of rating numbers

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2
Q

What does ‘log’ represent?

A

The number of 10s that are multiplied to create the original number

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3
Q

What is a decibel (dB)?

A

A common unit for measuring intensities

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4
Q

What is decibel notation?

A

A relative measurement and comparison expressed as a ratio

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5
Q

What is attenuation?

A

Decrease in intensity, power, and amplitude as sound travels

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6
Q

How is total attenuation calculated?

A

Total attenuation (dB) = AC X distance

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7
Q

What is amplification?

A

Increase in intensity, power, and amplitude as sound travels

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8
Q

What occurs during specular reflection?

A

Sound is reflected in only 1 direction in an organized manner when the boundary is smooth

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9
Q

What is diffuse reflection?

A

When a wave reflects off an irregular surface, radiating in more than one direction

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10
Q

Define scattering.

A

The random redirection of sound in many directions

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11
Q

What is Rayleigh scattering?

A

A special form of scattering that occurs when the structure’s dimensions are much smaller than the beam’s wavelength

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12
Q

What is absorption in the context of sound?

A

Conversion of ultrasonic energy into another energy form, such as heat

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13
Q

What is the attenuation coefficient (AC)?

A

The number of dBs of attenuation that occurs when sound travels 1cm

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14
Q

What is the formula for the half-value layer (HVL)?

A

HVL = f/2

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15
Q

What does the half-value layer (HVL) represent?

A

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

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16
Q

What are the typical values for half-value layer (HVL)?

A

0.25 - 1.0 cm

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17
Q

What is acoustic impedance?

A

The acoustic resistance to sound traveling in a medium

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18
Q

How is acoustic impedance calculated?

A

Density x speed

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19
Q

What units are used for acoustic impedance?

A

Rayls

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20
Q

What is a typical value for acoustic impedance?

A

1.25 - 1.75 Mrayls (MZ)

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21
Q

What is normal incidence?

A

When the incident sound beam strikes the boundary at exactly 90 degrees

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22
Q

What is oblique incidence?

A

When the incident sound beam strikes the boundary at any angle other than 90 degrees

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23
Q

What is incident intensity?

A

The sound wave’s intensity immediately before it strikes a boundary

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24
Q

What is reflected intensity?

A

The intensity of the portion of the incident beam that returns back after striking a boundary

25
Q

What is the definition of intensity in the context of sound waves?

A

The intensity of the portion of the incident beam that continues forward in the same general direction after striking a boundary.

26
Q

What does the intensity reflection coefficient (IRC) represent?

A

The percentage of the intensity that bounces back when a sound beam strikes the boundary between two media.

27
Q

What is the formula for calculating the intensity transmission coefficient (ITC)?

A

ITC = (transmitted intensity / incident intensity) x 100.

28
Q

What is the relationship between ITC and IRC?

A

ITC + IRC = 100%.

29
Q

What does Snell’s Law describe?

A

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

30
Q

What are the two conditions required for refraction to occur?

A
  • Different propagation speeds of the two media
  • Oblique incidence.
31
Q

What is the Half Value Layer in acoustics?

A

The distance at which the intensity of sound is reduced by half.

32
Q

What does an increase of 10 dB represent in terms of intensity?

A

Ten times larger intensity.

33
Q

What does a decrease of 10 dB represent in terms of intensity?

A

One-tenth of the original intensity.

34
Q

What is Rayleigh scattering?

A

A type of scattering that occurs when sound waves interact with small particles, resulting in diffuse or backscattering.

35
Q

What factors contribute to attenuation in sound waves?

A
  • Absorption
  • Scattering.
36
Q

True or False: High frequency sound travels shorter distances compared to low frequency sound due to more attenuation.

A

True.

37
Q

Fill in the blank: The angle of reflection equals the _______.

A

angle of incidence.

38
Q

What is the effect of higher frequencies on path length in sound propagation?

A

Higher frequencies result in shorter distances/path length.

39
Q

What is the significance of the transmission angle in relation to the speed of media?

A

sin(transmission angle) = speed of Medium 2 / speed of Medium 1.

40
Q

What does a high attenuation rate in media indicate?

A

It indicates that the media absorbs or scatters sound more effectively.

41
Q

What is meant by organized specular reflection?

A

Reflection that occurs in a predictable direction, typically at a smooth boundary.

42
Q

What characterizes disorganized scattering?

A

It leads to diffuse or backscattering of sound waves.

43
Q

What type of media generally has a low attenuation rate?

A

Fluids.

44
Q

What are the categories of differences in ultrasound media?

A
  • identical
  • slightly different
  • substantially different

These categories help to classify how ultrasound behaves in different media.

45
Q

What is the primary medium for ultrasound attenuation?

A

water

Water is often used as a reference medium for ultrasound studies.

46
Q

List some biologic fluids that can be involved in ultrasound.

A
  • blood
  • urine
  • biologic fluids

These fluids have varying properties that affect ultrasound transmission.

47
Q

Which tissue types are typically considered in ultrasound studies?

A
  • fat
  • soft tissue
  • muscle

Different tissues have different acoustic properties affecting ultrasound propagation.

48
Q

What are the impedance relationships between bone and lung?

A

different impedances required

This relationship is crucial for understanding ultrasound reflection and transmission.

49
Q

What are the possible speed relationships in ultrasound media?

A
  • Speed 2 = Speed 1
  • Speed 2 > Speed 1
  • Speed 2 < Speed 1

These relationships affect how ultrasound waves travel through different media.

50
Q

What event occurs when ultrasound waves change direction as they pass into a different medium?

A

Refraction

Refraction is important for understanding angles of transmission.

51
Q

What are the possible angles of transmission in ultrasound?

A
  • none
  • small
  • large

The angle of transmission can significantly impact the behavior of ultrasound waves.

52
Q

What is the condition for reflection with normal incidence?

A

no refraction; transmission angle = incident angle

This condition is essential for predictable ultrasound reflection.

53
Q

What describes reflection with oblique incidence?

A

transmission angle > incident angle

Reflection behavior changes with the angle of incidence.

54
Q

What is the attenuation of ultrasound in media described as?

A

extremely low

Understanding attenuation is crucial for interpreting ultrasound results.

55
Q

Fill in the blank: The requirement for higher attenuation is described as _______.

A

higher

Different tissues require different levels of attenuation for effective ultrasound imaging.

56
Q

What is required for reflection in ultrasound?

A

oblique incidence and different speeds required

This is critical for understanding how ultrasound waves behave at interfaces.

57
Q

What can be derived from reflection information in ultrasound?

A

derived from reflection information; use law of conservation of energy

This principle helps in analyzing ultrasound data.

58
Q

True or False: We can predict the outcomes of ultrasound reflection and transmission with absolute certainty.

A

False

The complexities of tissue interactions make predictions challenging.

Physics (24 decks)

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