Mod 1 Unit 3 (Sound Interaction With Matter) Flashcards
What is attenuation?
decrease in wave amplitude/power as it travels through a medium
Types of attenuation
Absorption, reflection/scattering, refraction
What is absorption?
main type of attenuation, energy into heat, non-linear exponential
Absorption depends on
medium type (viscosity) and frequency
A higher frequency does what to the attenuation, penetration, and resolution?
increases attenuation, decreases penetration, increases resolution
A lower frequency does what to the attenuation, penetration, and resolution?
decreases attenuation, increases penetration, decreases resolution
Higher viscosity means that
there is more energy to move molecules therefore more absorption
Water and fluid creates what artifact and why?
posterior enhancement artifact because the viscosity is low
Bone creates what artifact and why?
posterior shadowing artifact because the viscosity is high
Posterior shadowing occurs due to
high attenuation
Posterior enhancement occurs due to
low attenuation
What is acoustic impedance?
transfer of sound energy from one medium to another
No AI difference=
no reflection
AI Z value is based on what two factors?
density and propagation speed
What is reflection?
propagating wave changes direction with some loss of energy + AI changes
