Sound and media 2 Flashcards
How are scattering and absorption related to frequency?
Directly related
Does air have high or low attenuation?
high attenuation
What term is used to describe the distance sound travels in tissue that reduces the intensity of sound to one-half its original value?
Half-value layer thickness
What are the units for half-value layer thickness?
unit of length (cm)
What is half-value layer thickness also called?
- half-boundary layer
- depth of penetration
- penetration depth
What does half-value layer thickness depend upon?
medium & frequency
Does high or low frequency result in thick high-value layer?
Low frequency
Does high or low frequency result in thin half-value?
high frequency
Does media with a high attenuation have a thin or thick half- value?
thin half- value
Does media with a low attenuation have a thin or thick half-value?
thick half- value
What term is used to describe acoustic resistance to sound traveling through a medium?
impedance
What is crucial to the ability of ultrasound to image objects deep within the body?
transmission
What term in an important tissue property that influences the amount of reflection?
acoustic transmission
How is acoustic impedance calculated?
density of the medium x propagation speed
What does the reflection of a sound wave depend upon?
difference in acoustic impedance of the two media
True or false, a tissues impedance is measured not calculated.
False, a tissue’s impedance is CALCULATED not measured.
What are the units of impedance?
Rayls (z)
What is impedance determined by?
Medium
What is another name for acoustic impedance?
Characteristic impedances
What determines the behavior of a pulse
The angle at which a wave hits a boundary
What does an acute angle mean?
less than 90 degrees
What does a right angle mean?
exactly 90 degrees
What does an obtuse angle mean?
Greater 90 degrees
What are angles with measurements other than 90 degrees called?
oblique angles
True or false, both acute and obtuse angles are oblique angles?
True
What is the term used to describe a sound beam striking a boundary at exactly 90 degrees?
Normal indcidence
What are other terms for normal incidences?
- Perpendicular
- Orthogonal
- right angle
- 90 degree
What occurs when a sound beam strikes a boundary at any other angle than 90 degrees?
Oblique incidence
