Interaction Of Sound And Media Flashcards
What is a logarithm?
A novel method of rating numbers
What does ‘log’ represent?
The number of 10s that are multiplied to create the original number
What is a decibel (dB)?
A common unit for measuring intensities
What is decibel notation?
A relative measurement and comparison expressed as a ratio
What is attenuation?
Decrease in intensity, power, and amplitude as sound travels
How is total attenuation calculated?
Total attenuation (dB) = AC X distance
What is amplification?
Increase in intensity, power, and amplitude as sound travels
What occurs during specular reflection?
Sound is reflected in only 1 direction in an organized manner when the boundary is smooth
What is diffuse reflection?
When a wave reflects off an irregular surface, radiating in more than one direction
Define scattering.
The random redirection of sound in many directions
What is Rayleigh scattering?
A special form of scattering that occurs when the structure’s dimensions are much smaller than the beam’s wavelength
What is absorption in the context of sound?
Conversion of ultrasonic energy into another energy form, such as heat
What is the attenuation coefficient (AC)?
The number of dBs of attenuation that occurs when sound travels 1cm
What is the formula for the half-value layer (HVL)?
HVL = f/2
What does the half-value layer (HVL) represent?
The distance sound travels in a tissue that reduces the intensity of sound to one-half its original value
What are the typical values for half-value layer (HVL)?
0.25 - 1.0 cm
What is acoustic impedance?
The acoustic resistance to sound traveling in a medium
How is acoustic impedance calculated?
Density x speed
What units are used for acoustic impedance?
Rayls
What is a typical value for acoustic impedance?
1.25 - 1.75 Mrayls (MZ)
What is normal incidence?
When the incident sound beam strikes the boundary at exactly 90 degrees
What is oblique incidence?
When the incident sound beam strikes the boundary at any angle other than 90 degrees
What is incident intensity?
The sound wave’s intensity immediately before it strikes a boundary
What is reflected intensity?
The intensity of the portion of the incident beam that returns back after striking a boundary
What is the definition of intensity in the context of sound waves?
The intensity of the portion of the incident beam that continues forward in the same general direction after striking a boundary.
What does the intensity reflection coefficient (IRC) represent?
The percentage of the intensity that bounces back when a sound beam strikes the boundary between two media.
What is the formula for calculating the intensity transmission coefficient (ITC)?
ITC = (transmitted intensity / incident intensity) x 100.
What is the relationship between ITC and IRC?
ITC + IRC = 100%.
What does Snell’s Law describe?
The change in direction of wave propagation when traveling from one medium to another.
What are the two conditions required for refraction to occur?
- Different propagation speeds of the two media
- Oblique incidence.
What is the Half Value Layer in acoustics?
The distance at which the intensity of sound is reduced by half.
What does an increase of 10 dB represent in terms of intensity?
Ten times larger intensity.
What does a decrease of 10 dB represent in terms of intensity?
One-tenth of the original intensity.
What is Rayleigh scattering?
A type of scattering that occurs when sound waves interact with small particles, resulting in diffuse or backscattering.
What factors contribute to attenuation in sound waves?
- Absorption
- Scattering.
True or False: High frequency sound travels shorter distances compared to low frequency sound due to more attenuation.
True.
Fill in the blank: The angle of reflection equals the _______.
angle of incidence.
What is the effect of higher frequencies on path length in sound propagation?
Higher frequencies result in shorter distances/path length.
What is the significance of the transmission angle in relation to the speed of media?
sin(transmission angle) = speed of Medium 2 / speed of Medium 1.
What does a high attenuation rate in media indicate?
It indicates that the media absorbs or scatters sound more effectively.
What is meant by organized specular reflection?
Reflection that occurs in a predictable direction, typically at a smooth boundary.
What characterizes disorganized scattering?
It leads to diffuse or backscattering of sound waves.
What type of media generally has a low attenuation rate?
Fluids.
What are the categories of differences in ultrasound media?
- identical
- slightly different
- substantially different
These categories help to classify how ultrasound behaves in different media.
What is the primary medium for ultrasound attenuation?
water
Water is often used as a reference medium for ultrasound studies.
List some biologic fluids that can be involved in ultrasound.
- blood
- urine
- biologic fluids
These fluids have varying properties that affect ultrasound transmission.
Which tissue types are typically considered in ultrasound studies?
- fat
- soft tissue
- muscle
Different tissues have different acoustic properties affecting ultrasound propagation.
What are the impedance relationships between bone and lung?
different impedances required
This relationship is crucial for understanding ultrasound reflection and transmission.
What are the possible speed relationships in ultrasound media?
- Speed 2 = Speed 1
- Speed 2 > Speed 1
- Speed 2 < Speed 1
These relationships affect how ultrasound waves travel through different media.
What event occurs when ultrasound waves change direction as they pass into a different medium?
Refraction
Refraction is important for understanding angles of transmission.
What are the possible angles of transmission in ultrasound?
- none
- small
- large
The angle of transmission can significantly impact the behavior of ultrasound waves.
What is the condition for reflection with normal incidence?
no refraction; transmission angle = incident angle
This condition is essential for predictable ultrasound reflection.
What describes reflection with oblique incidence?
transmission angle > incident angle
Reflection behavior changes with the angle of incidence.
What is the attenuation of ultrasound in media described as?
extremely low
Understanding attenuation is crucial for interpreting ultrasound results.
Fill in the blank: The requirement for higher attenuation is described as _______.
higher
Different tissues require different levels of attenuation for effective ultrasound imaging.
What is required for reflection in ultrasound?
oblique incidence and different speeds required
This is critical for understanding how ultrasound waves behave at interfaces.
What can be derived from reflection information in ultrasound?
derived from reflection information; use law of conservation of energy
This principle helps in analyzing ultrasound data.
True or False: We can predict the outcomes of ultrasound reflection and transmission with absolute certainty.
False
The complexities of tissue interactions make predictions challenging.
