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28 Cards in this Set

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Attenuation, definition
is the weakening of a sound wave as it travels through the medium, decrease in intensity, power, and amplitude
State the relationship between attenuation and distance
direct, as path length increases, attenuation increases
State the relationship between attenuation and frequency
direct, as frequency increases, attenuation increases
reflection, definition
occurs when a portion of the wave's acoustic energy is redirected back towards the transducer when the sound strikes a boundary, it weakens the sound beam
two forms of reflection are
specular- when the boundary is smooth, the sound is reflected in only one direction in an organized manner
non-specular (diffuse or backscatter)- random reflection in multiple directions, from sound reflecting off irregular surface
rayleigh scattering, definition
occurs when the structure's dimension are much smaller than the beam's wavelength, it scatters the beam equally in all directions-ex RBC
state the relationship between rayleigh scattering and frequency
direct, as frequency increases rayleigh scattering increases
-rayleigh scattering=frequency to the fourth power
defintion of absorption
occurs when US energy is converted into another form of energy-like heat or mechanical vibration of intercellular particles
state the relationship between absorption and frequency
direct, as frequency increases absorption increases, in soft tissues 80% or more of total attenuation is caused by absorption
which form of reflection is the stongest, but is not reflected back towards the transducer?
specular reflection
definition of impedence
it is the acoustic resistance to sound traveling through a medium
what is the unit of impedence and its mathematical equation?
RAYLS (Z)
impedence=density x speed
impedence is calculated not measured
impedence is the property of what only?
the medium
state the relationship between density and impedence
direct, as density increases impedence increases
state the relationship between speed and impedence
direct, as speed increases impedence increases
state the definition of normal incidence
occurs when the sound beam strikes a boundary between different tissues at exactly 90 degrees
state the definition of oblique incidence
occurs when the sound beam strikes a boundary at angle other than 90 degrees-can be acute or obtuse
what is refraction?
change in direction of wave propagation when traveling from one medium to another, if the medium doesn't change then there is no refraction-therefore if incidence or speed doesn't change then no refraction
rayleigh scattering
rayleigh scattering
specular reflection
specular reflection
non specular reflection
non specular reflection
normal incidence
normal incidence
oblique incidence
oblique incidence
refraction
refraction
period
period
frequency
frequency
amplitude, compression and rarefaction
amplitude, compression and rarefaction
wavelength
wavelength