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28 Cards in this Set
- Front
- Back
Attenuation, definition
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is the weakening of a sound wave as it travels through the medium, decrease in intensity, power, and amplitude
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State the relationship between attenuation and distance
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direct, as path length increases, attenuation increases
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State the relationship between attenuation and frequency
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direct, as frequency increases, attenuation increases
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reflection, definition
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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
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two forms of reflection are
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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 |
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rayleigh scattering, definition
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occurs when the structure's dimension are much smaller than the beam's wavelength, it scatters the beam equally in all directions-ex RBC
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state the relationship between rayleigh scattering and frequency
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direct, as frequency increases rayleigh scattering increases
-rayleigh scattering=frequency to the fourth power |
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defintion of absorption
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occurs when US energy is converted into another form of energy-like heat or mechanical vibration of intercellular particles
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state the relationship between absorption and frequency
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direct, as frequency increases absorption increases, in soft tissues 80% or more of total attenuation is caused by absorption
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which form of reflection is the stongest, but is not reflected back towards the transducer?
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specular reflection
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definition of impedence
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it is the acoustic resistance to sound traveling through a medium
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what is the unit of impedence and its mathematical equation?
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RAYLS (Z)
impedence=density x speed impedence is calculated not measured |
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impedence is the property of what only?
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the medium
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state the relationship between density and impedence
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direct, as density increases impedence increases
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state the relationship between speed and impedence
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direct, as speed increases impedence increases
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state the definition of normal incidence
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occurs when the sound beam strikes a boundary between different tissues at exactly 90 degrees
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state the definition of oblique incidence
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occurs when the sound beam strikes a boundary at angle other than 90 degrees-can be acute or obtuse
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what is refraction?
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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
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rayleigh scattering
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rayleigh scattering
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specular reflection
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specular reflection
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non specular reflection
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non specular reflection
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normal incidence
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normal incidence
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oblique incidence
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oblique incidence
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refraction
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refraction
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period
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period
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frequency
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frequency
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amplitude, compression and rarefaction
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amplitude, compression and rarefaction
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wavelength
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wavelength
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