Interaction Of Sound And Media

Question 1

What is a logarithm?

Answer 1

A novel method of rating numbers

Question 2

What does ‘log’ represent?

Answer 2

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

Question 3

What is a decibel (dB)?

Answer 3

A common unit for measuring intensities

Question 4

What is decibel notation?

Answer 4

A relative measurement and comparison expressed as a ratio

Question 5

What is attenuation?

Answer 5

Decrease in intensity, power, and amplitude as sound travels

Question 6

How is total attenuation calculated?

Answer 6

Total attenuation (dB) = AC X distance

Question 7

What is amplification?

Answer 7

Increase in intensity, power, and amplitude as sound travels

Question 8

What occurs during specular reflection?

Answer 8

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

Question 9

What is diffuse reflection?

Answer 9

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

Question 10

Define scattering.

Answer 10

The random redirection of sound in many directions

Question 11

What is Rayleigh scattering?

Answer 11

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

Question 12

What is absorption in the context of sound?

Answer 12

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

Question 13

What is the attenuation coefficient (AC)?

Answer 13

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

Question 14

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

Answer 14

HVL = f/2

Question 15

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

Answer 15

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

Question 16

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

Answer 16

0.25 - 1.0 cm

Question 17

What is acoustic impedance?

Answer 17

The acoustic resistance to sound traveling in a medium

Question 18

How is acoustic impedance calculated?

Answer 18

Density x speed

Question 19

What units are used for acoustic impedance?

Answer 19

Rayls

Question 20

What is a typical value for acoustic impedance?

Answer 20

1.25 - 1.75 Mrayls (MZ)

Question 21

What is normal incidence?

Answer 21

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

Question 22

What is oblique incidence?

Answer 22

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

Question 23

What is incident intensity?

Answer 23

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

Question 24

What is reflected intensity?

Answer 24

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

Question 25

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

Answer 25

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

Question 26

What does the intensity reflection coefficient (IRC) represent?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

What is the relationship between ITC and IRC?

Answer 28

ITC + IRC = 100%.

Question 29

What does Snell's Law describe?

Answer 29

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

Question 30

What are the two conditions required for refraction to occur?

Answer 30

* Different propagation speeds of the two media * Oblique incidence.

Question 31

What is the Half Value Layer in acoustics?

Answer 31

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

Question 32

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

Answer 32

Ten times larger intensity.

Question 33

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

Answer 33

One-tenth of the original intensity.

Question 34

What is Rayleigh scattering?

Answer 34

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

Question 35

What factors contribute to attenuation in sound waves?

Answer 35

* Absorption * Scattering.

Question 36

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

Answer 36

True.

Question 37

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

Answer 37

angle of incidence.

Question 38

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

Answer 38

Higher frequencies result in shorter distances/path length.

Question 39

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

Answer 39

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

Question 40

What does a high attenuation rate in media indicate?

Answer 40

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

Question 41

What is meant by organized specular reflection?

Answer 41

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

Question 42

What characterizes disorganized scattering?

Answer 42

It leads to diffuse or backscattering of sound waves.

Question 43

What type of media generally has a low attenuation rate?

Answer 43

Fluids.

Question 44

What are the categories of differences in ultrasound media?

Answer 44

* identical * slightly different * substantially different ## Footnote These categories help to classify how ultrasound behaves in different media.

Question 45

What is the primary medium for ultrasound attenuation?

Answer 45

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

Question 46

List some biologic fluids that can be involved in ultrasound.

Answer 46

* blood * urine * biologic fluids ## Footnote These fluids have varying properties that affect ultrasound transmission.

Question 47

Which tissue types are typically considered in ultrasound studies?

Answer 47

* fat * soft tissue * muscle ## Footnote Different tissues have different acoustic properties affecting ultrasound propagation.

Question 48

What are the impedance relationships between bone and lung?

Answer 48

different impedances required ## Footnote This relationship is crucial for understanding ultrasound reflection and transmission.

Question 49

What are the possible speed relationships in ultrasound media?

Answer 49

* Speed 2 = Speed 1 * Speed 2 > Speed 1 * Speed 2 < Speed 1 ## Footnote These relationships affect how ultrasound waves travel through different media.

Question 50

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

Answer 50

Refraction ## Footnote Refraction is important for understanding angles of transmission.

Question 51

What are the possible angles of transmission in ultrasound?

Answer 51

* none * small * large ## Footnote The angle of transmission can significantly impact the behavior of ultrasound waves.

Question 52

What is the condition for reflection with normal incidence?

Answer 52

no refraction; transmission angle = incident angle ## Footnote This condition is essential for predictable ultrasound reflection.

Question 53

What describes reflection with oblique incidence?

Answer 53

transmission angle > incident angle ## Footnote Reflection behavior changes with the angle of incidence.

Question 54

What is the attenuation of ultrasound in media described as?

Answer 54

extremely low ## Footnote Understanding attenuation is crucial for interpreting ultrasound results.

Question 55

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

Answer 55

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

Question 56

What is required for reflection in ultrasound?

Answer 56

oblique incidence and different speeds required ## Footnote This is critical for understanding how ultrasound waves behave at interfaces.

Question 57

What can be derived from reflection information in ultrasound?

Answer 57

derived from reflection information; use law of conservation of energy ## Footnote This principle helps in analyzing ultrasound data.

Question 58

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

Answer 58

False ## Footnote The complexities of tissue interactions make predictions challenging.