Sound and media Flashcards
What does attenuation mean?
to weaken
What does amplification mean?
to strengthen
What does 3db mean
double
What does 10 db mean?
ten times greater
What does -3db mean?
half
What does -10db mean
one-tenth
As a sound wave propagates through a medium does it increase or decrease in intensity?
decrease in intensity
What term is used to describe the decrease in intensity, power, and amplitude as sound travels through a medium?
propagation
What is attenuation determined by
Path length and frequency of sound.
True or false, distance indirectly affects attenuation?
false, distance directly affects attenuation
As sound travels, does the attenuation become greater or smaller?
greater
As sound travels, does the beam become weaker or stronger?
weaker
How are distance and attenuation related?
directly
What does attenuation in soft tissue depend on?
frequency
How are frequency and attenuation related?
Greater
Is attenuation greater or lower in higher frequency?
Lower
Is attenuation greater or lower in lower frequency?
lower
How is attenuation measured?
Decibels
How is attenuation reported?
As a relative change
When imaging at a shallow depth is attenuation low or high?
Low
When imaging at a deep depth is attenuation low or high?
High
true or false, -10db has the same meaning as attenuating 10 db?
True
What processes contribute to attenuation?
- Reflection
- Absorption
- scattering
What weakens the portion of the sound wave that continues to move in the forward direction?
reflection
What occurs when dimensions of a boundary are large?
reflection
Whare are 2 forms of reflection?
- specular
- diffuse
True or false, specular reflection at an angle returns directly to the transducer?
False, They do Not return to the transducer
Is specular reflection organized or disorganizded?
Organized
When the boundary of an object is smooth, how is the sound reflected?
In one direction
What term is used when a wave reflects off an irregular surface and radiates in multiple directions?
Diffuse reflection or backscatter
What term is used for the random disorganized, chaotic redirection of sound?
scattering
When does sound wave scatter?
When tissue interface is small ( equal to or less the wavelength)
Do higher or lower frequency sound waves scatter more?
Higher
How is scattering related to frequency?
Directly related
What type of scattering occurs when a dimension of an object is much smaller than the beams wavelength?
Rayleigh related
True or false, rayleigh scattering redirects sound waves equally in all directions.
True
What type of scattering is seen with the interaction of ultrasound and red blood cells?
Rayleigh scattering
What is Rayleigh scattering proportional to?
Frequency
When you increase frequency, what happens to Rayleigh scattering?
increases
What occurs when ultrasonic energy is converted into another form of energy?
Absorption
how is absorption related to frequency?
Directly related
Do lower or higher frequency waves attenuate more?
higher frequency (due to absorption)
What does total attenuation depend on?
Frequency of sound tissue distance beam travels
What is the term used for reporting attenuation?
attenuation coefficient
What are the units of attenuation coefficient?
db/cm
True or False, attenuation, coefficient is the number of decibels of attenuation that occur when sound travels 10 centimeters?
False. The attention coefficient is the number of decibels of attenuation that occur when sound travels centimeter.
Does the value of the attenuation coefficient change when the path length changes?
No
What is the equation for total attenuation?
Attenuation coefficient x distance
Is sound travels at a depth of 8 cm, and the attenuation coefficient remains 2 db/cm, what is the total attenuation of the beam?
16 db (8 cm x 2 db/cm)
In soft tissue, how are attenuation coefficient and frequency related?
Directly related
true or false, attenuation coefficient is one-third of the frequency?
False. Attenuation coefficient is one-half of the frequency
What is the equation of attenuation in soft tissue?
Frequency/2
